Ignore:
Timestamp:
14/06/14 11:20:37 (8 years ago)
Author:
julian.reschke@…
Message:

update to latest version of rfc2629.xslt, regen all HTML

File:
1 edited

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  • draft-ietf-httpbis/19/p2-semantics.html

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    504507      <link rel="schema.dct" href="http://purl.org/dc/terms/">
    505508      <meta name="dct.creator" content="Fielding, R.">
     
    512515      <meta name="description" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request header fields, response status codes, and response header fields.">
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    515518      <table class="header">
    516519         <tbody>
     
    524527            </tr>
    525528            <tr>
    526                <td class="left">Obsoletes: <a href="http://tools.ietf.org/html/rfc2616">2616</a> (if approved)
     529               <td class="left">Obsoletes: <a href="https://tools.ietf.org/html/rfc2616">2616</a> (if approved)
    527530               </td>
    528531               <td class="right">Y. Lafon, Editor</td>
    529532            </tr>
    530533            <tr>
    531                <td class="left">Updates: <a href="http://tools.ietf.org/html/rfc2817">2817</a> (if approved)
     534               <td class="left">Updates: <a href="https://tools.ietf.org/html/rfc2817">2817</a> (if approved)
    532535               </td>
    533536               <td class="right">W3C</td>
     
    548551      </table>
    549552      <p class="title">HTTP/1.1, part 2: Message Semantics<br><span class="filename">draft-ietf-httpbis-p2-semantics-19</span></p>
    550       <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1> 
     553      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
    551554      <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information
    552555         systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the
    553556         seven-part specification that defines the protocol referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
    554       </p> 
     557      </p>
    555558      <p>Part 2 defines the semantics of HTTP messages as expressed by request methods, request header fields, response status codes,
    556559         and response header fields.
    557       </p> 
    558       <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1> 
     560      </p>
     561      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
    559562      <p>Discussion of this draft should take place on the HTTPBIS working group mailing list (ietf-http-wg@w3.org), which is archived
    560563         at &lt;<a href="http://lists.w3.org/Archives/Public/ietf-http-wg/">http://lists.w3.org/Archives/Public/ietf-http-wg/</a>&gt;.
    561       </p> 
     564      </p>
    562565      <p>The current issues list is at &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/report/3">http://tools.ietf.org/wg/httpbis/trac/report/3</a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href="http://tools.ietf.org/wg/httpbis/">http://tools.ietf.org/wg/httpbis/</a>&gt;.
    563       </p> 
     566      </p>
    564567      <p>The changes in this draft are summarized in <a href="#changes.since.18" title="Since draft-ietf-httpbis-p2-semantics-18">Appendix&nbsp;C.20</a>.
    565       </p>
    566       <h1><a id="rfc.status" href="#rfc.status">Status of This Memo</a></h1>
    567       <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
    568       <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
    569          working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href="http://datatracker.ietf.org/drafts/current/">http://datatracker.ietf.org/drafts/current/</a>.
    570568      </p>
    571       <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
    572          documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
    573          in progress”.
    574       </p>
    575       <p>This Internet-Draft will expire on September 13, 2012.</p>
    576       <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1>
    577       <p>Copyright © 2012 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
    578       <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
    579          and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
    580          text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
    581          BSD License.
    582       </p>
    583       <p>This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November
    584          10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to
    585          allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s)
    586          controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative
    587          works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate
    588          it into languages other than English.
    589       </p>
     569      <div id="rfc.status">
     570         <h1><a href="#rfc.status">Status of This Memo</a></h1>
     571         <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
     572         <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
     573            working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href="http://datatracker.ietf.org/drafts/current/">http://datatracker.ietf.org/drafts/current/</a>.
     574         </p>
     575         <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
     576            documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
     577            in progress”.
     578         </p>
     579         <p>This Internet-Draft will expire on September 13, 2012.</p>
     580      </div>
     581      <div id="rfc.copyrightnotice">
     582         <h1><a href="#rfc.copyrightnotice">Copyright Notice</a></h1>
     583         <p>Copyright © 2012 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
     584         <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
     585            and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
     586            text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
     587            BSD License.
     588         </p>
     589         <p>This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November
     590            10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to
     591            allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s)
     592            controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative
     593            works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate
     594            it into languages other than English.
     595         </p>
     596      </div>
    590597      <hr class="noprint">
    591598      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
    592599      <ul class="toc">
    593          <li>1.&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
    594                <li>1.1&nbsp;&nbsp;&nbsp;<a href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></li>
    595                <li>1.2&nbsp;&nbsp;&nbsp;<a href="#notation">Syntax Notation</a><ul>
    596                      <li>1.2.1&nbsp;&nbsp;&nbsp;<a href="#core.rules">Core Rules</a></li>
    597                      <li>1.2.2&nbsp;&nbsp;&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li>
     600         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
     601               <li><a href="#rfc.section.1.1">1.1</a>&nbsp;&nbsp;&nbsp;<a href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></li>
     602               <li><a href="#rfc.section.1.2">1.2</a>&nbsp;&nbsp;&nbsp;<a href="#notation">Syntax Notation</a><ul>
     603                     <li><a href="#rfc.section.1.2.1">1.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#core.rules">Core Rules</a></li>
     604                     <li><a href="#rfc.section.1.2.2">1.2.2</a>&nbsp;&nbsp;&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li>
    598605                  </ul>
    599606               </li>
    600607            </ul>
    601608         </li>
    602          <li>2.&nbsp;&nbsp;&nbsp;<a href="#method">Method</a><ul>
    603                <li>2.1&nbsp;&nbsp;&nbsp;<a href="#overview.of.methods">Overview of Methods</a></li>
    604                <li>2.2&nbsp;&nbsp;&nbsp;<a href="#method.registry">Method Registry</a><ul>
    605                      <li>2.2.1&nbsp;&nbsp;&nbsp;<a href="#considerations.for.new.methods">Considerations for New Methods</a></li>
     609         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#method">Method</a><ul>
     610               <li><a href="#rfc.section.2.1">2.1</a>&nbsp;&nbsp;&nbsp;<a href="#overview.of.methods">Overview of Methods</a></li>
     611               <li><a href="#rfc.section.2.2">2.2</a>&nbsp;&nbsp;&nbsp;<a href="#method.registry">Method Registry</a><ul>
     612                     <li><a href="#rfc.section.2.2.1">2.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#considerations.for.new.methods">Considerations for New Methods</a></li>
    606613                  </ul>
    607614               </li>
    608615            </ul>
    609616         </li>
    610          <li>3.&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Fields</a><ul>
    611                <li>3.1&nbsp;&nbsp;&nbsp;<a href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></li>
    612                <li>3.2&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li>
    613                <li>3.3&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li>
     617         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Fields</a><ul>
     618               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></li>
     619               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li>
     620               <li><a href="#rfc.section.3.3">3.3</a>&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li>
    614621            </ul>
    615622         </li>
    616          <li>4.&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a><ul>
    617                <li>4.1&nbsp;&nbsp;&nbsp;<a href="#overview.of.status.codes">Overview of Status Codes</a></li>
    618                <li>4.2&nbsp;&nbsp;&nbsp;<a href="#status.code.registry">Status Code Registry</a><ul>
    619                      <li>4.2.1&nbsp;&nbsp;&nbsp;<a href="#considerations.for.new.status.codes">Considerations for New Status Codes</a></li>
     623         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a><ul>
     624               <li><a href="#rfc.section.4.1">4.1</a>&nbsp;&nbsp;&nbsp;<a href="#overview.of.status.codes">Overview of Status Codes</a></li>
     625               <li><a href="#rfc.section.4.2">4.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.registry">Status Code Registry</a><ul>
     626                     <li><a href="#rfc.section.4.2.1">4.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#considerations.for.new.status.codes">Considerations for New Status Codes</a></li>
    620627                  </ul>
    621628               </li>
    622629            </ul>
    623630         </li>
    624          <li>5.&nbsp;&nbsp;&nbsp;<a href="#representation">Representation</a><ul>
    625                <li>5.1&nbsp;&nbsp;&nbsp;<a href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></li>
     631         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#representation">Representation</a><ul>
     632               <li><a href="#rfc.section.5.1">5.1</a>&nbsp;&nbsp;&nbsp;<a href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></li>
    626633            </ul>
    627634         </li>
    628          <li>6.&nbsp;&nbsp;&nbsp;<a href="#method.definitions">Method Definitions</a><ul>
    629                <li>6.1&nbsp;&nbsp;&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a><ul>
    630                      <li>6.1.1&nbsp;&nbsp;&nbsp;<a href="#safe.methods">Safe Methods</a></li>
    631                      <li>6.1.2&nbsp;&nbsp;&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></li>
     635         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#method.definitions">Method Definitions</a><ul>
     636               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a><ul>
     637                     <li><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#safe.methods">Safe Methods</a></li>
     638                     <li><a href="#rfc.section.6.1.2">6.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></li>
    632639                  </ul>
    633640               </li>
    634                <li>6.2&nbsp;&nbsp;&nbsp;<a href="#OPTIONS">OPTIONS</a></li>
    635                <li>6.3&nbsp;&nbsp;&nbsp;<a href="#GET">GET</a></li>
    636                <li>6.4&nbsp;&nbsp;&nbsp;<a href="#HEAD">HEAD</a></li>
    637                <li>6.5&nbsp;&nbsp;&nbsp;<a href="#POST">POST</a></li>
    638                <li>6.6&nbsp;&nbsp;&nbsp;<a href="#PUT">PUT</a></li>
    639                <li>6.7&nbsp;&nbsp;&nbsp;<a href="#DELETE">DELETE</a></li>
    640                <li>6.8&nbsp;&nbsp;&nbsp;<a href="#TRACE">TRACE</a></li>
    641                <li>6.9&nbsp;&nbsp;&nbsp;<a href="#CONNECT">CONNECT</a></li>
     641               <li><a href="#rfc.section.6.2">6.2</a>&nbsp;&nbsp;&nbsp;<a href="#OPTIONS">OPTIONS</a></li>
     642               <li><a href="#rfc.section.6.3">6.3</a>&nbsp;&nbsp;&nbsp;<a href="#GET">GET</a></li>
     643               <li><a href="#rfc.section.6.4">6.4</a>&nbsp;&nbsp;&nbsp;<a href="#HEAD">HEAD</a></li>
     644               <li><a href="#rfc.section.6.5">6.5</a>&nbsp;&nbsp;&nbsp;<a href="#POST">POST</a></li>
     645               <li><a href="#rfc.section.6.6">6.6</a>&nbsp;&nbsp;&nbsp;<a href="#PUT">PUT</a></li>
     646               <li><a href="#rfc.section.6.7">6.7</a>&nbsp;&nbsp;&nbsp;<a href="#DELETE">DELETE</a></li>
     647               <li><a href="#rfc.section.6.8">6.8</a>&nbsp;&nbsp;&nbsp;<a href="#TRACE">TRACE</a></li>
     648               <li><a href="#rfc.section.6.9">6.9</a>&nbsp;&nbsp;&nbsp;<a href="#CONNECT">CONNECT</a></li>
    642649            </ul>
    643650         </li>
    644          <li>7.&nbsp;&nbsp;&nbsp;<a href="#status.codes">Status Code Definitions</a><ul>
    645                <li>7.1&nbsp;&nbsp;&nbsp;<a href="#status.1xx">Informational 1xx</a><ul>
    646                      <li>7.1.1&nbsp;&nbsp;&nbsp;<a href="#status.100">100 Continue</a></li>
    647                      <li>7.1.2&nbsp;&nbsp;&nbsp;<a href="#status.101">101 Switching Protocols</a></li>
     651         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#status.codes">Status Code Definitions</a><ul>
     652               <li><a href="#rfc.section.7.1">7.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.1xx">Informational 1xx</a><ul>
     653                     <li><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.100">100 Continue</a></li>
     654                     <li><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.101">101 Switching Protocols</a></li>
    648655                  </ul>
    649656               </li>
    650                <li>7.2&nbsp;&nbsp;&nbsp;<a href="#status.2xx">Successful 2xx</a><ul>
    651                      <li>7.2.1&nbsp;&nbsp;&nbsp;<a href="#status.200">200 OK</a></li>
    652                      <li>7.2.2&nbsp;&nbsp;&nbsp;<a href="#status.201">201 Created</a></li>
    653                      <li>7.2.3&nbsp;&nbsp;&nbsp;<a href="#status.202">202 Accepted</a></li>
    654                      <li>7.2.4&nbsp;&nbsp;&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></li>
    655                      <li>7.2.5&nbsp;&nbsp;&nbsp;<a href="#status.204">204 No Content</a></li>
    656                      <li>7.2.6&nbsp;&nbsp;&nbsp;<a href="#status.205">205 Reset Content</a></li>
     657               <li><a href="#rfc.section.7.2">7.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.2xx">Successful 2xx</a><ul>
     658                     <li><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.200">200 OK</a></li>
     659                     <li><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.201">201 Created</a></li>
     660                     <li><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.202">202 Accepted</a></li>
     661                     <li><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></li>
     662                     <li><a href="#rfc.section.7.2.5">7.2.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.204">204 No Content</a></li>
     663                     <li><a href="#rfc.section.7.2.6">7.2.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.205">205 Reset Content</a></li>
    657664                  </ul>
    658665               </li>
    659                <li>7.3&nbsp;&nbsp;&nbsp;<a href="#status.3xx">Redirection 3xx</a><ul>
    660                      <li>7.3.1&nbsp;&nbsp;&nbsp;<a href="#status.300">300 Multiple Choices</a></li>
    661                      <li>7.3.2&nbsp;&nbsp;&nbsp;<a href="#status.301">301 Moved Permanently</a></li>
    662                      <li>7.3.3&nbsp;&nbsp;&nbsp;<a href="#status.302">302 Found</a></li>
    663                      <li>7.3.4&nbsp;&nbsp;&nbsp;<a href="#status.303">303 See Other</a></li>
    664                      <li>7.3.5&nbsp;&nbsp;&nbsp;<a href="#status.305">305 Use Proxy</a></li>
    665                      <li>7.3.6&nbsp;&nbsp;&nbsp;<a href="#status.306">306 (Unused)</a></li>
    666                      <li>7.3.7&nbsp;&nbsp;&nbsp;<a href="#status.307">307 Temporary Redirect</a></li>
     666               <li><a href="#rfc.section.7.3">7.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.3xx">Redirection 3xx</a><ul>
     667                     <li><a href="#rfc.section.7.3.1">7.3.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.300">300 Multiple Choices</a></li>
     668                     <li><a href="#rfc.section.7.3.2">7.3.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.301">301 Moved Permanently</a></li>
     669                     <li><a href="#rfc.section.7.3.3">7.3.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.302">302 Found</a></li>
     670                     <li><a href="#rfc.section.7.3.4">7.3.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.303">303 See Other</a></li>
     671                     <li><a href="#rfc.section.7.3.5">7.3.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.305">305 Use Proxy</a></li>
     672                     <li><a href="#rfc.section.7.3.6">7.3.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.306">306 (Unused)</a></li>
     673                     <li><a href="#rfc.section.7.3.7">7.3.7</a>&nbsp;&nbsp;&nbsp;<a href="#status.307">307 Temporary Redirect</a></li>
    667674                  </ul>
    668675               </li>
    669                <li>7.4&nbsp;&nbsp;&nbsp;<a href="#status.4xx">Client Error 4xx</a><ul>
    670                      <li>7.4.1&nbsp;&nbsp;&nbsp;<a href="#status.400">400 Bad Request</a></li>
    671                      <li>7.4.2&nbsp;&nbsp;&nbsp;<a href="#status.402">402 Payment Required</a></li>
    672                      <li>7.4.3&nbsp;&nbsp;&nbsp;<a href="#status.403">403 Forbidden</a></li>
    673                      <li>7.4.4&nbsp;&nbsp;&nbsp;<a href="#status.404">404 Not Found</a></li>
    674                      <li>7.4.5&nbsp;&nbsp;&nbsp;<a href="#status.405">405 Method Not Allowed</a></li>
    675                      <li>7.4.6&nbsp;&nbsp;&nbsp;<a href="#status.406">406 Not Acceptable</a></li>
    676                      <li>7.4.7&nbsp;&nbsp;&nbsp;<a href="#status.408">408 Request Timeout</a></li>
    677                      <li>7.4.8&nbsp;&nbsp;&nbsp;<a href="#status.409">409 Conflict</a></li>
    678                      <li>7.4.9&nbsp;&nbsp;&nbsp;<a href="#status.410">410 Gone</a></li>
    679                      <li>7.4.10&nbsp;&nbsp;&nbsp;<a href="#status.411">411 Length Required</a></li>
    680                      <li>7.4.11&nbsp;&nbsp;&nbsp;<a href="#status.413">413 Request Representation Too Large</a></li>
    681                      <li>7.4.12&nbsp;&nbsp;&nbsp;<a href="#status.414">414 URI Too Long</a></li>
    682                      <li>7.4.13&nbsp;&nbsp;&nbsp;<a href="#status.415">415 Unsupported Media Type</a></li>
    683                      <li>7.4.14&nbsp;&nbsp;&nbsp;<a href="#status.417">417 Expectation Failed</a></li>
    684                      <li>7.4.15&nbsp;&nbsp;&nbsp;<a href="#status.426">426 Upgrade Required</a></li>
     676               <li><a href="#rfc.section.7.4">7.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.4xx">Client Error 4xx</a><ul>
     677                     <li><a href="#rfc.section.7.4.1">7.4.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.400">400 Bad Request</a></li>
     678                     <li><a href="#rfc.section.7.4.2">7.4.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.402">402 Payment Required</a></li>
     679                     <li><a href="#rfc.section.7.4.3">7.4.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.403">403 Forbidden</a></li>
     680                     <li><a href="#rfc.section.7.4.4">7.4.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.404">404 Not Found</a></li>
     681                     <li><a href="#rfc.section.7.4.5">7.4.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.405">405 Method Not Allowed</a></li>
     682                     <li><a href="#rfc.section.7.4.6">7.4.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.406">406 Not Acceptable</a></li>
     683                     <li><a href="#rfc.section.7.4.7">7.4.7</a>&nbsp;&nbsp;&nbsp;<a href="#status.408">408 Request Timeout</a></li>
     684                     <li><a href="#rfc.section.7.4.8">7.4.8</a>&nbsp;&nbsp;&nbsp;<a href="#status.409">409 Conflict</a></li>
     685                     <li><a href="#rfc.section.7.4.9">7.4.9</a>&nbsp;&nbsp;&nbsp;<a href="#status.410">410 Gone</a></li>
     686                     <li><a href="#rfc.section.7.4.10">7.4.10</a>&nbsp;&nbsp;&nbsp;<a href="#status.411">411 Length Required</a></li>
     687                     <li><a href="#rfc.section.7.4.11">7.4.11</a>&nbsp;&nbsp;&nbsp;<a href="#status.413">413 Request Representation Too Large</a></li>
     688                     <li><a href="#rfc.section.7.4.12">7.4.12</a>&nbsp;&nbsp;&nbsp;<a href="#status.414">414 URI Too Long</a></li>
     689                     <li><a href="#rfc.section.7.4.13">7.4.13</a>&nbsp;&nbsp;&nbsp;<a href="#status.415">415 Unsupported Media Type</a></li>
     690                     <li><a href="#rfc.section.7.4.14">7.4.14</a>&nbsp;&nbsp;&nbsp;<a href="#status.417">417 Expectation Failed</a></li>
     691                     <li><a href="#rfc.section.7.4.15">7.4.15</a>&nbsp;&nbsp;&nbsp;<a href="#status.426">426 Upgrade Required</a></li>
    685692                  </ul>
    686693               </li>
    687                <li>7.5&nbsp;&nbsp;&nbsp;<a href="#status.5xx">Server Error 5xx</a><ul>
    688                      <li>7.5.1&nbsp;&nbsp;&nbsp;<a href="#status.500">500 Internal Server Error</a></li>
    689                      <li>7.5.2&nbsp;&nbsp;&nbsp;<a href="#status.501">501 Not Implemented</a></li>
    690                      <li>7.5.3&nbsp;&nbsp;&nbsp;<a href="#status.502">502 Bad Gateway</a></li>
    691                      <li>7.5.4&nbsp;&nbsp;&nbsp;<a href="#status.503">503 Service Unavailable</a></li>
    692                      <li>7.5.5&nbsp;&nbsp;&nbsp;<a href="#status.504">504 Gateway Timeout</a></li>
    693                      <li>7.5.6&nbsp;&nbsp;&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></li>
     694               <li><a href="#rfc.section.7.5">7.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.5xx">Server Error 5xx</a><ul>
     695                     <li><a href="#rfc.section.7.5.1">7.5.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.500">500 Internal Server Error</a></li>
     696                     <li><a href="#rfc.section.7.5.2">7.5.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.501">501 Not Implemented</a></li>
     697                     <li><a href="#rfc.section.7.5.3">7.5.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.502">502 Bad Gateway</a></li>
     698                     <li><a href="#rfc.section.7.5.4">7.5.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.503">503 Service Unavailable</a></li>
     699                     <li><a href="#rfc.section.7.5.5">7.5.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.504">504 Gateway Timeout</a></li>
     700                     <li><a href="#rfc.section.7.5.6">7.5.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></li>
    694701                  </ul>
    695702               </li>
    696703            </ul>
    697704         </li>
    698          <li>8.&nbsp;&nbsp;&nbsp;<a href="#http.date">Date/Time Formats</a></li>
    699          <li>9.&nbsp;&nbsp;&nbsp;<a href="#product.tokens">Product Tokens</a></li>
    700          <li>10.&nbsp;&nbsp;&nbsp;<a href="#header.field.definitions">Header Field Definitions</a><ul>
    701                <li>10.1&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
    702                <li>10.2&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a></li>
    703                <li>10.3&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
    704                <li>10.4&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
    705                <li>10.5&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
    706                <li>10.6&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
    707                <li>10.7&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
    708                <li>10.8&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
    709                <li>10.9&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
    710                <li>10.10&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
     705         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#http.date">Date/Time Formats</a></li>
     706         <li><a href="#rfc.section.9">9.</a>&nbsp;&nbsp;&nbsp;<a href="#product.tokens">Product Tokens</a></li>
     707         <li><a href="#rfc.section.10">10.</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.definitions">Header Field Definitions</a><ul>
     708               <li><a href="#rfc.section.10.1">10.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
     709               <li><a href="#rfc.section.10.2">10.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a></li>
     710               <li><a href="#rfc.section.10.3">10.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
     711               <li><a href="#rfc.section.10.4">10.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
     712               <li><a href="#rfc.section.10.5">10.5</a>&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
     713               <li><a href="#rfc.section.10.6">10.6</a>&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
     714               <li><a href="#rfc.section.10.7">10.7</a>&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
     715               <li><a href="#rfc.section.10.8">10.8</a>&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
     716               <li><a href="#rfc.section.10.9">10.9</a>&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
     717               <li><a href="#rfc.section.10.10">10.10</a>&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
    711718            </ul>
    712719         </li>
    713          <li>11.&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
    714                <li>11.1&nbsp;&nbsp;&nbsp;<a href="#method.registration">Method Registry</a></li>
    715                <li>11.2&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registry</a></li>
    716                <li>11.3&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
     720         <li><a href="#rfc.section.11">11.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
     721               <li><a href="#rfc.section.11.1">11.1</a>&nbsp;&nbsp;&nbsp;<a href="#method.registration">Method Registry</a></li>
     722               <li><a href="#rfc.section.11.2">11.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registry</a></li>
     723               <li><a href="#rfc.section.11.3">11.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
    717724            </ul>
    718725         </li>
    719          <li>12.&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
    720                <li>12.1&nbsp;&nbsp;&nbsp;<a href="#security.sensitive">Transfer of Sensitive Information</a></li>
    721                <li>12.2&nbsp;&nbsp;&nbsp;<a href="#encoding.sensitive.information.in.uris">Encoding Sensitive Information in URIs</a></li>
    722                <li>12.3&nbsp;&nbsp;&nbsp;<a href="#location.spoofing-leakage">Location Header Fields: Spoofing and Information Leakage</a></li>
    723                <li>12.4&nbsp;&nbsp;&nbsp;<a href="#rfc.section.12.4">Security Considerations for CONNECT</a></li>
     726         <li><a href="#rfc.section.12">12.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
     727               <li><a href="#rfc.section.12.1">12.1</a>&nbsp;&nbsp;&nbsp;<a href="#security.sensitive">Transfer of Sensitive Information</a></li>
     728               <li><a href="#rfc.section.12.2">12.2</a>&nbsp;&nbsp;&nbsp;<a href="#encoding.sensitive.information.in.uris">Encoding Sensitive Information in URIs</a></li>
     729               <li><a href="#rfc.section.12.3">12.3</a>&nbsp;&nbsp;&nbsp;<a href="#location.spoofing-leakage">Location Header Fields: Spoofing and Information Leakage</a></li>
     730               <li><a href="#rfc.section.12.4">12.4</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.12.4">Security Considerations for CONNECT</a></li>
    724731            </ul>
    725732         </li>
    726          <li>13.&nbsp;&nbsp;&nbsp;<a href="#acks">Acknowledgments</a></li>
    727          <li>14.&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
    728                <li>14.1&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
    729                <li>14.2&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
     733         <li><a href="#rfc.section.13">13.</a>&nbsp;&nbsp;&nbsp;<a href="#acks">Acknowledgments</a></li>
     734         <li><a href="#rfc.section.14">14.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
     735               <li><a href="#rfc.section.14.1">14.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
     736               <li><a href="#rfc.section.14.2">14.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
    730737            </ul>
    731738         </li>
    732          <li><a href="#rfc.authors">Authors' Addresses</a></li>
    733          <li>A.&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
    734          <li>B.&nbsp;&nbsp;&nbsp;<a href="#collected.abnf">Collected ABNF</a></li>
    735          <li>C.&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
    736                <li>C.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.1">Since RFC 2616</a></li>
    737                <li>C.2&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.2">Since draft-ietf-httpbis-p2-semantics-00</a></li>
    738                <li>C.3&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.3">Since draft-ietf-httpbis-p2-semantics-01</a></li>
    739                <li>C.4&nbsp;&nbsp;&nbsp;<a href="#changes.since.02">Since draft-ietf-httpbis-p2-semantics-02</a></li>
    740                <li>C.5&nbsp;&nbsp;&nbsp;<a href="#changes.since.03">Since draft-ietf-httpbis-p2-semantics-03</a></li>
    741                <li>C.6&nbsp;&nbsp;&nbsp;<a href="#changes.since.04">Since draft-ietf-httpbis-p2-semantics-04</a></li>
    742                <li>C.7&nbsp;&nbsp;&nbsp;<a href="#changes.since.05">Since draft-ietf-httpbis-p2-semantics-05</a></li>
    743                <li>C.8&nbsp;&nbsp;&nbsp;<a href="#changes.since.06">Since draft-ietf-httpbis-p2-semantics-06</a></li>
    744                <li>C.9&nbsp;&nbsp;&nbsp;<a href="#changes.since.07">Since draft-ietf-httpbis-p2-semantics-07</a></li>
    745                <li>C.10&nbsp;&nbsp;&nbsp;<a href="#changes.since.08">Since draft-ietf-httpbis-p2-semantics-08</a></li>
    746                <li>C.11&nbsp;&nbsp;&nbsp;<a href="#changes.since.09">Since draft-ietf-httpbis-p2-semantics-09</a></li>
    747                <li>C.12&nbsp;&nbsp;&nbsp;<a href="#changes.since.10">Since draft-ietf-httpbis-p2-semantics-10</a></li>
    748                <li>C.13&nbsp;&nbsp;&nbsp;<a href="#changes.since.11">Since draft-ietf-httpbis-p2-semantics-11</a></li>
    749                <li>C.14&nbsp;&nbsp;&nbsp;<a href="#changes.since.12">Since draft-ietf-httpbis-p2-semantics-12</a></li>
    750                <li>C.15&nbsp;&nbsp;&nbsp;<a href="#changes.since.13">Since draft-ietf-httpbis-p2-semantics-13</a></li>
    751                <li>C.16&nbsp;&nbsp;&nbsp;<a href="#changes.since.14">Since draft-ietf-httpbis-p2-semantics-14</a></li>
    752                <li>C.17&nbsp;&nbsp;&nbsp;<a href="#changes.since.15">Since draft-ietf-httpbis-p2-semantics-15</a></li>
    753                <li>C.18&nbsp;&nbsp;&nbsp;<a href="#changes.since.16">Since draft-ietf-httpbis-p2-semantics-16</a></li>
    754                <li>C.19&nbsp;&nbsp;&nbsp;<a href="#changes.since.17">Since draft-ietf-httpbis-p2-semantics-17</a></li>
    755                <li>C.20&nbsp;&nbsp;&nbsp;<a href="#changes.since.18">Since draft-ietf-httpbis-p2-semantics-18</a></li>
     739         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
     740         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#collected.abnf">Collected ABNF</a></li>
     741         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
     742               <li><a href="#rfc.section.C.1">C.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.1">Since RFC 2616</a></li>
     743               <li><a href="#rfc.section.C.2">C.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.2">Since draft-ietf-httpbis-p2-semantics-00</a></li>
     744               <li><a href="#rfc.section.C.3">C.3</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.3">Since draft-ietf-httpbis-p2-semantics-01</a></li>
     745               <li><a href="#rfc.section.C.4">C.4</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.02">Since draft-ietf-httpbis-p2-semantics-02</a></li>
     746               <li><a href="#rfc.section.C.5">C.5</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.03">Since draft-ietf-httpbis-p2-semantics-03</a></li>
     747               <li><a href="#rfc.section.C.6">C.6</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.04">Since draft-ietf-httpbis-p2-semantics-04</a></li>
     748               <li><a href="#rfc.section.C.7">C.7</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.05">Since draft-ietf-httpbis-p2-semantics-05</a></li>
     749               <li><a href="#rfc.section.C.8">C.8</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.06">Since draft-ietf-httpbis-p2-semantics-06</a></li>
     750               <li><a href="#rfc.section.C.9">C.9</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.07">Since draft-ietf-httpbis-p2-semantics-07</a></li>
     751               <li><a href="#rfc.section.C.10">C.10</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.08">Since draft-ietf-httpbis-p2-semantics-08</a></li>
     752               <li><a href="#rfc.section.C.11">C.11</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.09">Since draft-ietf-httpbis-p2-semantics-09</a></li>
     753               <li><a href="#rfc.section.C.12">C.12</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.10">Since draft-ietf-httpbis-p2-semantics-10</a></li>
     754               <li><a href="#rfc.section.C.13">C.13</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.11">Since draft-ietf-httpbis-p2-semantics-11</a></li>
     755               <li><a href="#rfc.section.C.14">C.14</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.12">Since draft-ietf-httpbis-p2-semantics-12</a></li>
     756               <li><a href="#rfc.section.C.15">C.15</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.13">Since draft-ietf-httpbis-p2-semantics-13</a></li>
     757               <li><a href="#rfc.section.C.16">C.16</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.14">Since draft-ietf-httpbis-p2-semantics-14</a></li>
     758               <li><a href="#rfc.section.C.17">C.17</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.15">Since draft-ietf-httpbis-p2-semantics-15</a></li>
     759               <li><a href="#rfc.section.C.18">C.18</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.16">Since draft-ietf-httpbis-p2-semantics-16</a></li>
     760               <li><a href="#rfc.section.C.19">C.19</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.17">Since draft-ietf-httpbis-p2-semantics-17</a></li>
     761               <li><a href="#rfc.section.C.20">C.20</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.18">Since draft-ietf-httpbis-p2-semantics-18</a></li>
    756762            </ul>
    757763         </li>
    758764         <li><a href="#rfc.index">Index</a></li>
     765         <li><a href="#rfc.authors">Authors' Addresses</a></li>
    759766      </ul>
    760       <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a id="introduction" href="#introduction">Introduction</a></h1>
    761       <p id="rfc.section.1.p.1">This document defines HTTP/1.1 request and response semantics. Each HTTP message, as defined in <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, is in the form of either a request or a response. An HTTP server listens on a connection for HTTP requests and responds
    762          to each request, in the order received on that connection, with one or more HTTP response messages. This document defines
    763          the commonly agreed upon semantics of the HTTP uniform interface, the intentions defined by each request method, and the various
    764          response messages that might be expected as a result of applying that method to the target resource.
    765       </p>
    766       <p id="rfc.section.1.p.2">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
    767          errata changes. A future draft will reorganize the sections to better reflect the content. In particular, the sections will
    768          be ordered according to the typical processing of an HTTP request message (after message parsing): resource mapping, methods,
    769          request modifying header fields, response status, status modifying header fields, and resource metadata. The current mess
    770          reflects how widely dispersed these topics and associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    771       </p>
    772       <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a id="intro.conformance.and.error.handling" href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></h2>
    773       <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
    774          in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
    775       </p>
    776       <p id="rfc.section.1.1.p.2">This document defines conformance criteria for several roles in HTTP communication, including Senders, Recipients, Clients,
    777          Servers, User-Agents, Origin Servers, Intermediaries, Proxies and Gateways. See <a href="p1-messaging.html#architecture" title="Architecture">Section 2</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for definitions of these terms.
    778       </p>
    779       <p id="rfc.section.1.1.p.3">An implementation is considered conformant if it complies with all of the requirements associated with its role(s). Note that
    780          SHOULD-level requirements are relevant here, unless one of the documented exceptions is applicable.
    781       </p>
    782       <p id="rfc.section.1.1.p.4">This document also uses ABNF to define valid protocol elements (<a href="#notation" title="Syntax Notation">Section&nbsp;1.2</a>). In addition to the prose requirements placed upon them, Senders <em class="bcp14">MUST NOT</em> generate protocol elements that are invalid.
    783       </p>
    784       <p id="rfc.section.1.1.p.5">Unless noted otherwise, Recipients <em class="bcp14">MAY</em> take steps to recover a usable protocol element from an invalid construct. However, HTTP does not define specific error handling
    785          mechanisms, except in cases where it has direct impact on security. This is because different uses of the protocol require
    786          different error handling strategies; for example, a Web browser may wish to transparently recover from a response where the
    787          Location header field doesn't parse according to the ABNF, whereby in a systems control protocol using HTTP, this type of
    788          error recovery could lead to dangerous consequences.
    789       </p>
    790       <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a id="notation" href="#notation">Syntax Notation</a></h2>
    791       <p id="rfc.section.1.2.p.1">This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> with the list rule extension defined in <a href="p1-messaging.html#notation" title="Syntax Notation">Section 1.2</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. <a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;B</a> shows the collected ABNF with the list rule expanded.
    792       </p>
    793       <p id="rfc.section.1.2.p.2">The following core rules are included by reference, as defined in <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>, <a href="http://tools.ietf.org/html/rfc5234#appendix-B.1">Appendix B.1</a>: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG
    794          (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR
    795          (any visible US-ASCII character).
    796       </p>
    797       <h3 id="rfc.section.1.2.1"><a href="#rfc.section.1.2.1">1.2.1</a>&nbsp;<a id="core.rules" href="#core.rules">Core Rules</a></h3>
    798       <p id="rfc.section.1.2.1.p.1">The core rules below are defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>:
    799       </p>
    800       <div id="rfc.figure.u.1"></div><pre class="inline">  <a href="#core.rules" class="smpl">BWS</a>           = &lt;BWS, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
     767      <div id="introduction">
     768         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a href="#introduction">Introduction</a></h1>
     769         <p id="rfc.section.1.p.1">This document defines HTTP/1.1 request and response semantics. Each HTTP message, as defined in <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, is in the form of either a request or a response. An HTTP server listens on a connection for HTTP requests and responds
     770            to each request, in the order received on that connection, with one or more HTTP response messages. This document defines
     771            the commonly agreed upon semantics of the HTTP uniform interface, the intentions defined by each request method, and the various
     772            response messages that might be expected as a result of applying that method to the target resource.
     773         </p>
     774         <p id="rfc.section.1.p.2">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
     775            errata changes. A future draft will reorganize the sections to better reflect the content. In particular, the sections will
     776            be ordered according to the typical processing of an HTTP request message (after message parsing): resource mapping, methods,
     777            request modifying header fields, response status, status modifying header fields, and resource metadata. The current mess
     778            reflects how widely dispersed these topics and associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
     779         </p>
     780         <div id="intro.conformance.and.error.handling">
     781            <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></h2>
     782            <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
     783               in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
     784            </p>
     785            <p id="rfc.section.1.1.p.2">This document defines conformance criteria for several roles in HTTP communication, including Senders, Recipients, Clients,
     786               Servers, User-Agents, Origin Servers, Intermediaries, Proxies and Gateways. See <a href="p1-messaging.html#architecture" title="Architecture">Section 2</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for definitions of these terms.
     787            </p>
     788            <p id="rfc.section.1.1.p.3">An implementation is considered conformant if it complies with all of the requirements associated with its role(s). Note that
     789               SHOULD-level requirements are relevant here, unless one of the documented exceptions is applicable.
     790            </p>
     791            <p id="rfc.section.1.1.p.4">This document also uses ABNF to define valid protocol elements (<a href="#notation" title="Syntax Notation">Section&nbsp;1.2</a>). In addition to the prose requirements placed upon them, Senders <em class="bcp14">MUST NOT</em> generate protocol elements that are invalid.
     792            </p>
     793            <p id="rfc.section.1.1.p.5">Unless noted otherwise, Recipients <em class="bcp14">MAY</em> take steps to recover a usable protocol element from an invalid construct. However, HTTP does not define specific error handling
     794               mechanisms, except in cases where it has direct impact on security. This is because different uses of the protocol require
     795               different error handling strategies; for example, a Web browser may wish to transparently recover from a response where the
     796               Location header field doesn't parse according to the ABNF, whereby in a systems control protocol using HTTP, this type of
     797               error recovery could lead to dangerous consequences.
     798            </p>
     799         </div>
     800         <div id="notation">
     801            <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a href="#notation">Syntax Notation</a></h2>
     802            <p id="rfc.section.1.2.p.1">This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> with the list rule extension defined in <a href="p1-messaging.html#notation" title="Syntax Notation">Section 1.2</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. <a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;B</a> shows the collected ABNF with the list rule expanded.
     803            </p>
     804            <p id="rfc.section.1.2.p.2">The following core rules are included by reference, as defined in <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>, <a href="https://tools.ietf.org/html/rfc5234#appendix-B.1">Appendix B.1</a>: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG
     805               (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR
     806               (any visible US-ASCII character).
     807            </p>
     808            <div id="core.rules">
     809               <h3 id="rfc.section.1.2.1"><a href="#rfc.section.1.2.1">1.2.1</a>&nbsp;<a href="#core.rules">Core Rules</a></h3>
     810               <p id="rfc.section.1.2.1.p.1">The core rules below are defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>:
     811               </p>
     812               <div id="rfc.figure.u.1"></div><pre class="inline">  <a href="#core.rules" class="smpl">BWS</a>           = &lt;BWS, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
    801813  <a href="#core.rules" class="smpl">OWS</a>           = &lt;OWS, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
    802814  <a href="#core.rules" class="smpl">RWS</a>           = &lt;RWS, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
     
    804816  <a href="#core.rules" class="smpl">quoted-string</a> = &lt;quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a>&gt;
    805817  <a href="#core.rules" class="smpl">token</a>         = &lt;token, defined in <a href="#Part1" id="rfc.xref.Part1.10"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a>&gt;
    806 </pre><h3 id="rfc.section.1.2.2"><a href="#rfc.section.1.2.2">1.2.2</a>&nbsp;<a id="abnf.dependencies" href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h3>
    807       <p id="rfc.section.1.2.2.p.1">The ABNF rules below are defined in other parts:</p>
    808       <div id="rfc.figure.u.2"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">absolute-URI</a>  = &lt;absolute-URI, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.7</a>&gt;
     818</pre></div>
     819            <div id="abnf.dependencies">
     820               <h3 id="rfc.section.1.2.2"><a href="#rfc.section.1.2.2">1.2.2</a>&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h3>
     821               <p id="rfc.section.1.2.2.p.1">The ABNF rules below are defined in other parts:</p>
     822               <div id="rfc.figure.u.2"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">absolute-URI</a>  = &lt;absolute-URI, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.7</a>&gt;
    809823  <a href="#abnf.dependencies" class="smpl">comment</a>       = &lt;comment, defined in <a href="#Part1" id="rfc.xref.Part1.12"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a>&gt;
    810824  <a href="#abnf.dependencies" class="smpl">partial-URI</a>   = &lt;partial-URI, defined in <a href="#Part1" id="rfc.xref.Part1.13"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.7</a>&gt;
    811825  <a href="#abnf.dependencies" class="smpl">URI-reference</a> = &lt;URI-reference, defined in <a href="#Part1" id="rfc.xref.Part1.14"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.7</a>&gt;
    812 </pre><h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a id="method" href="#method">Method</a></h1>
    813       <p id="rfc.section.2.p.1">The method token indicates the request method to be performed on the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.15"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). The method is case-sensitive.
    814       </p>
    815       <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.1"></span>  <a href="#method" class="smpl">method</a>         = <a href="#core.rules" class="smpl">token</a>
     826</pre></div>
     827         </div>
     828      </div>
     829      <div id="method">
     830         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a href="#method">Method</a></h1>
     831         <p id="rfc.section.2.p.1">The method token indicates the request method to be performed on the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.15"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). The method is case-sensitive.
     832         </p>
     833         <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.1"></span>  <a href="#method" class="smpl">method</a>         = <a href="#core.rules" class="smpl">token</a>
    816834</pre><p id="rfc.section.2.p.3">The list of methods allowed by a resource can be specified in an Allow header field (<a href="#header.allow" id="rfc.xref.header.allow.1" title="Allow">Section&nbsp;10.1</a>). The status code of the response always notifies the client whether a method is currently allowed on a resource, since the
    817          set of allowed methods can change dynamically. An origin server <em class="bcp14">SHOULD</em> respond with the status code 405 (Method Not Allowed) if the method is known by the origin server but not allowed for the
    818          resource, and 501 (Not Implemented) if the method is unrecognized or not implemented by the origin server. The methods GET
    819          and HEAD <em class="bcp14">MUST</em> be supported by all general-purpose servers. All other methods are <em class="bcp14">OPTIONAL</em>; however, if the above methods are implemented, they <em class="bcp14">MUST</em> be implemented with the same semantics as those specified in <a href="#method.definitions" title="Method Definitions">Section&nbsp;6</a>.
    820       </p>
    821       <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a id="overview.of.methods" href="#overview.of.methods">Overview of Methods</a></h2>
    822       <p id="rfc.section.2.1.p.1">The methods listed below are defined in <a href="#method.definitions" title="Method Definitions">Section&nbsp;6</a>.
    823       </p>
    824       <div id="rfc.table.u.1">
    825          <table class="tt full left" cellpadding="3" cellspacing="0">
    826             <thead>
    827                <tr>
    828                   <th>Method Name</th>
    829                   <th>Defined in...</th>
    830                </tr>
    831             </thead>
    832             <tbody>
    833                <tr>
    834                   <td class="left">OPTIONS</td>
    835                   <td class="left"><a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;6.2</a></td>
    836                </tr>
    837                <tr>
    838                   <td class="left">GET</td>
    839                   <td class="left"><a href="#GET" id="rfc.xref.GET.1" title="GET">Section&nbsp;6.3</a></td>
    840                </tr>
    841                <tr>
    842                   <td class="left">HEAD</td>
    843                   <td class="left"><a href="#HEAD" id="rfc.xref.HEAD.1" title="HEAD">Section&nbsp;6.4</a></td>
    844                </tr>
    845                <tr>
    846                   <td class="left">POST</td>
    847                   <td class="left"><a href="#POST" id="rfc.xref.POST.1" title="POST">Section&nbsp;6.5</a></td>
    848                </tr>
    849                <tr>
    850                   <td class="left">PUT</td>
    851                   <td class="left"><a href="#PUT" id="rfc.xref.PUT.1" title="PUT">Section&nbsp;6.6</a></td>
    852                </tr>
    853                <tr>
    854                   <td class="left">DELETE</td>
    855                   <td class="left"><a href="#DELETE" id="rfc.xref.DELETE.1" title="DELETE">Section&nbsp;6.7</a></td>
    856                </tr>
    857                <tr>
    858                   <td class="left">TRACE</td>
    859                   <td class="left"><a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;6.8</a></td>
    860                </tr>
    861                <tr>
    862                   <td class="left">CONNECT</td>
    863                   <td class="left"><a href="#CONNECT" id="rfc.xref.CONNECT.1" title="CONNECT">Section&nbsp;6.9</a></td>
    864                </tr>
    865             </tbody>
    866          </table>
     835            set of allowed methods can change dynamically. An origin server <em class="bcp14">SHOULD</em> respond with the status code 405 (Method Not Allowed) if the method is known by the origin server but not allowed for the
     836            resource, and 501 (Not Implemented) if the method is unrecognized or not implemented by the origin server. The methods GET
     837            and HEAD <em class="bcp14">MUST</em> be supported by all general-purpose servers. All other methods are <em class="bcp14">OPTIONAL</em>; however, if the above methods are implemented, they <em class="bcp14">MUST</em> be implemented with the same semantics as those specified in <a href="#method.definitions" title="Method Definitions">Section&nbsp;6</a>.
     838         </p>
     839         <div id="overview.of.methods">
     840            <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a href="#overview.of.methods">Overview of Methods</a></h2>
     841            <p id="rfc.section.2.1.p.1">The methods listed below are defined in <a href="#method.definitions" title="Method Definitions">Section&nbsp;6</a>.
     842            </p>
     843            <div id="rfc.table.u.1">
     844               <table class="tt full left" cellpadding="3" cellspacing="0">
     845                  <thead>
     846                     <tr>
     847                        <th>Method Name</th>
     848                        <th>Defined in...</th>
     849                     </tr>
     850                  </thead>
     851                  <tbody>
     852                     <tr>
     853                        <td class="left">OPTIONS</td>
     854                        <td class="left"><a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;6.2</a></td>
     855                     </tr>
     856                     <tr>
     857                        <td class="left">GET</td>
     858                        <td class="left"><a href="#GET" id="rfc.xref.GET.1" title="GET">Section&nbsp;6.3</a></td>
     859                     </tr>
     860                     <tr>
     861                        <td class="left">HEAD</td>
     862                        <td class="left"><a href="#HEAD" id="rfc.xref.HEAD.1" title="HEAD">Section&nbsp;6.4</a></td>
     863                     </tr>
     864                     <tr>
     865                        <td class="left">POST</td>
     866                        <td class="left"><a href="#POST" id="rfc.xref.POST.1" title="POST">Section&nbsp;6.5</a></td>
     867                     </tr>
     868                     <tr>
     869                        <td class="left">PUT</td>
     870                        <td class="left"><a href="#PUT" id="rfc.xref.PUT.1" title="PUT">Section&nbsp;6.6</a></td>
     871                     </tr>
     872                     <tr>
     873                        <td class="left">DELETE</td>
     874                        <td class="left"><a href="#DELETE" id="rfc.xref.DELETE.1" title="DELETE">Section&nbsp;6.7</a></td>
     875                     </tr>
     876                     <tr>
     877                        <td class="left">TRACE</td>
     878                        <td class="left"><a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;6.8</a></td>
     879                     </tr>
     880                     <tr>
     881                        <td class="left">CONNECT</td>
     882                        <td class="left"><a href="#CONNECT" id="rfc.xref.CONNECT.1" title="CONNECT">Section&nbsp;6.9</a></td>
     883                     </tr>
     884                  </tbody>
     885               </table>
     886            </div>
     887            <p id="rfc.section.2.1.p.2">Note that this list is not exhaustive — it does not include request methods defined in other specifications.</p>
     888         </div>
     889         <div id="method.registry">
     890            <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a href="#method.registry">Method Registry</a></h2>
     891            <p id="rfc.section.2.2.p.1">The HTTP Method Registry defines the name space for the method token in the Request line of an HTTP request.</p>
     892            <p id="rfc.section.2.2.p.2">Registrations <em class="bcp14">MUST</em> include the following fields:
     893            </p>
     894            <ul>
     895               <li>Method Name (see <a href="#method" title="Method">Section&nbsp;2</a>)
     896               </li>
     897               <li>Safe ("yes" or "no", see <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>)
     898               </li>
     899               <li>Pointer to specification text</li>
     900            </ul>
     901            <p id="rfc.section.2.2.p.3">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.1"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="https://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
     902            </p>
     903            <p id="rfc.section.2.2.p.4">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-methods">http://www.iana.org/assignments/http-methods</a>&gt;.
     904            </p>
     905            <div id="considerations.for.new.methods">
     906               <h3 id="rfc.section.2.2.1"><a href="#rfc.section.2.2.1">2.2.1</a>&nbsp;<a href="#considerations.for.new.methods">Considerations for New Methods</a></h3>
     907               <p id="rfc.section.2.2.1.p.1">When it is necessary to express new semantics for a HTTP request that aren't specific to a single application or media type,
     908                  and currently defined methods are inadequate, it may be appropriate to register a new method.
     909               </p>
     910               <p id="rfc.section.2.2.1.p.2">HTTP methods are generic; that is, they are potentially applicable to any resource, not just one particular media type, "type"
     911                  of resource, or application. As such, it is preferred that new HTTP methods be registered in a document that isn't specific
     912                  to a single application, so that this is clear.
     913               </p>
     914               <p id="rfc.section.2.2.1.p.3">Due to the parsing rules defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.16"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, definitions of HTTP methods cannot prohibit the presence of a message body on either the request or the response message
     915                  (with responses to HEAD requests being the single exception). Definitions of new methods cannot change this rule, but they
     916                  can specify that only zero-length bodies (as opposed to absent bodies) are allowed.
     917               </p>
     918               <p id="rfc.section.2.2.1.p.4">New method definitions need to indicate whether they are safe (<a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>), what semantics (if any) the request body has, and whether they are idempotent (<a href="#idempotent.methods" title="Idempotent Methods">Section&nbsp;6.1.2</a>). They also need to state whether they can be cached (<a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>); in particular what conditions a cache may store the response, and under what conditions such a stored response may be used
     919                  to satisfy a subsequent request.
     920               </p>
     921            </div>
     922         </div>
    867923      </div>
    868       <p id="rfc.section.2.1.p.2">Note that this list is not exhaustive — it does not include request methods defined in other specifications.</p>
    869       <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a id="method.registry" href="#method.registry">Method Registry</a></h2>
    870       <p id="rfc.section.2.2.p.1">The HTTP Method Registry defines the name space for the method token in the Request line of an HTTP request.</p>
    871       <p id="rfc.section.2.2.p.2">Registrations <em class="bcp14">MUST</em> include the following fields:
    872       </p>
    873       <ul>
    874          <li>Method Name (see <a href="#method" title="Method">Section&nbsp;2</a>)
    875          </li>
    876          <li>Safe ("yes" or "no", see <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>)
    877          </li>
    878          <li>Pointer to specification text</li>
    879       </ul>
    880       <p id="rfc.section.2.2.p.3">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.1"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="http://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
    881       </p>
    882       <p id="rfc.section.2.2.p.4">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-methods">http://www.iana.org/assignments/http-methods</a>&gt;.
    883       </p>
    884       <h3 id="rfc.section.2.2.1"><a href="#rfc.section.2.2.1">2.2.1</a>&nbsp;<a id="considerations.for.new.methods" href="#considerations.for.new.methods">Considerations for New Methods</a></h3>
    885       <p id="rfc.section.2.2.1.p.1">When it is necessary to express new semantics for a HTTP request that aren't specific to a single application or media type,
    886          and currently defined methods are inadequate, it may be appropriate to register a new method.
    887       </p>
    888       <p id="rfc.section.2.2.1.p.2">HTTP methods are generic; that is, they are potentially applicable to any resource, not just one particular media type, "type"
    889          of resource, or application. As such, it is preferred that new HTTP methods be registered in a document that isn't specific
    890          to a single application, so that this is clear.
    891       </p>
    892       <p id="rfc.section.2.2.1.p.3">Due to the parsing rules defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.16"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, definitions of HTTP methods cannot prohibit the presence of a message body on either the request or the response message
    893          (with responses to HEAD requests being the single exception). Definitions of new methods cannot change this rule, but they
    894          can specify that only zero-length bodies (as opposed to absent bodies) are allowed.
    895       </p>
    896       <p id="rfc.section.2.2.1.p.4">New method definitions need to indicate whether they are safe (<a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>), what semantics (if any) the request body has, and whether they are idempotent (<a href="#idempotent.methods" title="Idempotent Methods">Section&nbsp;6.1.2</a>). They also need to state whether they can be cached (<a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>); in particular what conditions a cache may store the response, and under what conditions such a stored response may be used
    897          to satisfy a subsequent request.
    898       </p>
    899       <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="header.fields" href="#header.fields">Header Fields</a></h1>
    900       <p id="rfc.section.3.p.1">Header fields are key value pairs that can be used to communicate data about the message, its payload, the target resource,
    901          or about the connection itself (i.e., control data). See <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for a general definition of their syntax.
    902       </p>
    903       <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a id="considerations.for.creating.header.fields" href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></h2>
    904       <p id="rfc.section.3.1.p.1">New header fields are registered using the procedures described in <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>.
    905       </p>
    906       <p id="rfc.section.3.1.p.2">The requirements for header field names are defined in <a href="http://tools.ietf.org/html/rfc3864#section-4.1">Section 4.1</a> of <a href="#RFC3864" id="rfc.xref.RFC3864.2"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>. Authors of specifications defining new fields are advised to keep the name as short as practical, and not to prefix them
    907          with "X-" if they are to be registered (either immediately or in the future).
    908       </p>
    909       <p id="rfc.section.3.1.p.3">New header field values typically have their syntax defined using ABNF (<a href="#RFC5234" id="rfc.xref.RFC5234.3"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>), using the extension defined in <a href="p1-messaging.html#abnf.extension" title="ABNF list extension: #rule">Section 3.2.5</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> as necessary, and are usually constrained to the range of ASCII characters. Header fields needing a greater range of characters
    910          can use an encoding such as the one defined in <a href="#RFC5987" id="rfc.xref.RFC5987.1"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>.
    911       </p>
    912       <p id="rfc.section.3.1.p.4">Because commas (",") are used as a generic delimiter between field-values, they need to be treated with care if they are allowed
    913          in the field-value's payload. Typically, components that might contain a comma are protected with double-quotes using the
    914          quoted-string ABNF production (<a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a> of <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    915       </p>
    916       <p id="rfc.section.3.1.p.5">For example, a textual date and a URI (either of which might contain a comma) could be safely carried in field-values like
    917          these:
    918       </p>
    919       <div id="rfc.figure.u.4"></div><pre class="text">  Example-URI-Field: "http://example.com/a.html,foo",
     924      <div id="header.fields">
     925         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a href="#header.fields">Header Fields</a></h1>
     926         <p id="rfc.section.3.p.1">Header fields are key value pairs that can be used to communicate data about the message, its payload, the target resource,
     927            or about the connection itself (i.e., control data). See <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for a general definition of their syntax.
     928         </p>
     929         <div id="considerations.for.creating.header.fields">
     930            <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a href="#considerations.for.creating.header.fields">Considerations for Creating Header Fields</a></h2>
     931            <p id="rfc.section.3.1.p.1">New header fields are registered using the procedures described in <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>.
     932            </p>
     933            <p id="rfc.section.3.1.p.2">The requirements for header field names are defined in <a href="https://tools.ietf.org/html/rfc3864#section-4.1">Section 4.1</a> of <a href="#RFC3864" id="rfc.xref.RFC3864.2"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>. Authors of specifications defining new fields are advised to keep the name as short as practical, and not to prefix them
     934               with "X-" if they are to be registered (either immediately or in the future).
     935            </p>
     936            <p id="rfc.section.3.1.p.3">New header field values typically have their syntax defined using ABNF (<a href="#RFC5234" id="rfc.xref.RFC5234.3"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>), using the extension defined in <a href="p1-messaging.html#abnf.extension" title="ABNF list extension: #rule">Section 3.2.5</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> as necessary, and are usually constrained to the range of ASCII characters. Header fields needing a greater range of characters
     937               can use an encoding such as the one defined in <a href="#RFC5987" id="rfc.xref.RFC5987.1"><cite title="Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters">[RFC5987]</cite></a>.
     938            </p>
     939            <p id="rfc.section.3.1.p.4">Because commas (",") are used as a generic delimiter between field-values, they need to be treated with care if they are allowed
     940               in the field-value's payload. Typically, components that might contain a comma are protected with double-quotes using the
     941               quoted-string ABNF production (<a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a> of <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     942            </p>
     943            <p id="rfc.section.3.1.p.5">For example, a textual date and a URI (either of which might contain a comma) could be safely carried in field-values like
     944               these:
     945            </p>
     946            <div id="rfc.figure.u.4"></div><pre class="text">  Example-URI-Field: "http://example.com/a.html,foo",
    920947                     "http://without-a-comma.example.com/"
    921948  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
    922949</pre><p id="rfc.section.3.1.p.7">Note that double quote delimiters almost always are used with the quoted-string production; using a different syntax inside
    923          double quotes will likely cause unnecessary confusion.
    924       </p>
    925       <p id="rfc.section.3.1.p.8">Many header fields use a format including (case-insensitively) named parameters (for instance, Content-Type, defined in <a href="p3-payload.html#header.content-type" title="Content-Type">Section 6.8</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). Allowing both unquoted (token) and quoted (quoted-string) syntax for the parameter value enables recipients to use existing
    926          parser components. When allowing both forms, the meaning of a parameter value ought to be independent of the syntax used for
    927          it (for an example, see the notes on parameter handling for media types in <a href="p3-payload.html#media.types" title="Media Types">Section 2.3</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
    928       </p>
    929       <p id="rfc.section.3.1.p.9">Authors of specifications defining new header fields are advised to consider documenting: </p>
    930       <ul>
    931          <li>
    932             <p>Whether the field is a single value, or whether it can be a list (delimited by commas; see <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    933             </p>
    934             <p>If it does not use the list syntax, document how to treat messages where the header field occurs multiple times (a sensible
    935                default would be to ignore the header field, but this might not always be the right choice).
    936             </p>
    937             <p>Note that intermediaries and software libraries might combine multiple header field instances into a single one, despite the
    938                header field not allowing this. A robust format enables recipients to discover these situations (good example: "Content-Type",
    939                as the comma can only appear inside quoted strings; bad example: "Location", as a comma can occur inside a URI).
    940             </p>
    941          </li>
    942          <li>
    943             <p>Under what conditions the header field can be used; e.g., only in responses or requests, in all messages, only on responses
    944                to a particular request method.
    945             </p>
    946          </li>
    947          <li>
    948             <p>Whether it is appropriate to list the field-name in the Connection header (i.e., if the header is to be hop-by-hop, see <a href="p1-messaging.html#header.connection" title="Connection">Section 6.1</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    949             </p>
    950          </li>
    951          <li>
    952             <p>Under what conditions intermediaries are allowed to modify the header field's value, insert or delete it.</p>
    953          </li>
    954          <li>
    955             <p>How the header might interact with caching (see <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    956             </p>
    957          </li>
    958          <li>
    959             <p>Whether the header field is useful or allowable in trailers (see <a href="p1-messaging.html#chunked.encoding" title="Chunked Transfer Coding">Section 4.1</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    960             </p>
    961          </li>
    962          <li>
    963             <p>Whether the header field should be preserved across redirects.</p>
    964          </li>
    965       </ul>
    966       <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="request.header.fields" href="#request.header.fields">Request Header Fields</a></h2>
    967       <p id="rfc.section.3.2.p.1">The request header fields allow the client to pass additional information about the request, and about the client itself,
    968          to the server. These fields act as request modifiers, with semantics equivalent to the parameters on a programming language
    969          method invocation.
    970       </p>
    971       <div id="rfc.table.u.2">
    972          <table class="tt full left" cellpadding="3" cellspacing="0">
    973             <thead>
    974                <tr>
    975                   <th>Header Field Name</th>
    976                   <th>Defined in...</th>
    977                </tr>
    978             </thead>
    979             <tbody>
    980                <tr>
    981                   <td class="left">Accept</td>
    982                   <td class="left"><a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a> of <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
    983                </tr>
    984                <tr>
    985                   <td class="left">Accept-Charset</td>
    986                   <td class="left"><a href="p3-payload.html#header.accept-charset" title="Accept-Charset">Section 6.2</a> of <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
    987                </tr>
    988                <tr>
    989                   <td class="left">Accept-Encoding</td>
    990                   <td class="left"><a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a> of <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
    991                </tr>
    992                <tr>
    993                   <td class="left">Accept-Language</td>
    994                   <td class="left"><a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a> of <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
    995                </tr>
    996                <tr>
    997                   <td class="left">Authorization</td>
    998                   <td class="left"><a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a> of <a href="#Part7" id="rfc.xref.Part7.1"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    999                </tr>
    1000                <tr>
    1001                   <td class="left">Expect</td>
    1002                   <td class="left"><a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;10.3</a></td>
    1003                </tr>
    1004                <tr>
    1005                   <td class="left">From</td>
    1006                   <td class="left"><a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;10.4</a></td>
    1007                </tr>
    1008                <tr>
    1009                   <td class="left">Host</td>
    1010                   <td class="left"><a href="p1-messaging.html#header.host" title="Host">Section 5.4</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td>
    1011                </tr>
    1012                <tr>
    1013                   <td class="left">If-Match</td>
    1014                   <td class="left"><a href="p4-conditional.html#header.if-match" title="If-Match">Section 3.1</a> of <a href="#Part4" id="rfc.xref.Part4.1"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1015                </tr>
    1016                <tr>
    1017                   <td class="left">If-Modified-Since</td>
    1018                   <td class="left"><a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 3.3</a> of <a href="#Part4" id="rfc.xref.Part4.2"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1019                </tr>
    1020                <tr>
    1021                   <td class="left">If-None-Match</td>
    1022                   <td class="left"><a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 3.2</a> of <a href="#Part4" id="rfc.xref.Part4.3"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1023                </tr>
    1024                <tr>
    1025                   <td class="left">If-Range</td>
    1026                   <td class="left"><a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a> of <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
    1027                </tr>
    1028                <tr>
    1029                   <td class="left">If-Unmodified-Since</td>
    1030                   <td class="left"><a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 3.4</a> of <a href="#Part4" id="rfc.xref.Part4.4"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1031                </tr>
    1032                <tr>
    1033                   <td class="left">Max-Forwards</td>
    1034                   <td class="left"><a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;10.6</a></td>
    1035                </tr>
    1036                <tr>
    1037                   <td class="left">Proxy-Authorization</td>
    1038                   <td class="left"><a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a> of <a href="#Part7" id="rfc.xref.Part7.2"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    1039                </tr>
    1040                <tr>
    1041                   <td class="left">Range</td>
    1042                   <td class="left"><a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.2"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
    1043                </tr>
    1044                <tr>
    1045                   <td class="left">Referer</td>
    1046                   <td class="left"><a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;10.7</a></td>
    1047                </tr>
    1048                <tr>
    1049                   <td class="left">TE</td>
    1050                   <td class="left"><a href="p1-messaging.html#header.te" title="TE">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td>
    1051                </tr>
    1052                <tr>
    1053                   <td class="left">User-Agent</td>
    1054                   <td class="left"><a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;10.10</a></td>
    1055                </tr>
    1056             </tbody>
    1057          </table>
     950               double quotes will likely cause unnecessary confusion.
     951            </p>
     952            <p id="rfc.section.3.1.p.8">Many header fields use a format including (case-insensitively) named parameters (for instance, Content-Type, defined in <a href="p3-payload.html#header.content-type" title="Content-Type">Section 6.8</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). Allowing both unquoted (token) and quoted (quoted-string) syntax for the parameter value enables recipients to use existing
     953               parser components. When allowing both forms, the meaning of a parameter value ought to be independent of the syntax used for
     954               it (for an example, see the notes on parameter handling for media types in <a href="p3-payload.html#media.types" title="Media Types">Section 2.3</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
     955            </p>
     956            <p id="rfc.section.3.1.p.9">Authors of specifications defining new header fields are advised to consider documenting: </p>
     957            <ul>
     958               <li>
     959                  <p>Whether the field is a single value, or whether it can be a list (delimited by commas; see <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     960                  </p>
     961                  <p>If it does not use the list syntax, document how to treat messages where the header field occurs multiple times (a sensible
     962                     default would be to ignore the header field, but this might not always be the right choice).
     963                  </p>
     964                  <p>Note that intermediaries and software libraries might combine multiple header field instances into a single one, despite the
     965                     header field not allowing this. A robust format enables recipients to discover these situations (good example: "Content-Type",
     966                     as the comma can only appear inside quoted strings; bad example: "Location", as a comma can occur inside a URI).
     967                  </p>
     968               </li>
     969               <li>
     970                  <p>Under what conditions the header field can be used; e.g., only in responses or requests, in all messages, only on responses
     971                     to a particular request method.
     972                  </p>
     973               </li>
     974               <li>
     975                  <p>Whether it is appropriate to list the field-name in the Connection header (i.e., if the header is to be hop-by-hop, see <a href="p1-messaging.html#header.connection" title="Connection">Section 6.1</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     976                  </p>
     977               </li>
     978               <li>
     979                  <p>Under what conditions intermediaries are allowed to modify the header field's value, insert or delete it.</p>
     980               </li>
     981               <li>
     982                  <p>How the header might interact with caching (see <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
     983                  </p>
     984               </li>
     985               <li>
     986                  <p>Whether the header field is useful or allowable in trailers (see <a href="p1-messaging.html#chunked.encoding" title="Chunked Transfer Coding">Section 4.1</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     987                  </p>
     988               </li>
     989               <li>
     990                  <p>Whether the header field should be preserved across redirects.</p>
     991               </li>
     992            </ul>
     993         </div>
     994         <div id="request.header.fields">
     995            <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a href="#request.header.fields">Request Header Fields</a></h2>
     996            <p id="rfc.section.3.2.p.1">The request header fields allow the client to pass additional information about the request, and about the client itself,
     997               to the server. These fields act as request modifiers, with semantics equivalent to the parameters on a programming language
     998               method invocation.
     999            </p>
     1000            <div id="rfc.table.u.2">
     1001               <table class="tt full left" cellpadding="3" cellspacing="0">
     1002                  <thead>
     1003                     <tr>
     1004                        <th>Header Field Name</th>
     1005                        <th>Defined in...</th>
     1006                     </tr>
     1007                  </thead>
     1008                  <tbody>
     1009                     <tr>
     1010                        <td class="left">Accept</td>
     1011                        <td class="left"><a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a> of <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
     1012                     </tr>
     1013                     <tr>
     1014                        <td class="left">Accept-Charset</td>
     1015                        <td class="left"><a href="p3-payload.html#header.accept-charset" title="Accept-Charset">Section 6.2</a> of <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
     1016                     </tr>
     1017                     <tr>
     1018                        <td class="left">Accept-Encoding</td>
     1019                        <td class="left"><a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a> of <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
     1020                     </tr>
     1021                     <tr>
     1022                        <td class="left">Accept-Language</td>
     1023                        <td class="left"><a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a> of <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a></td>
     1024                     </tr>
     1025                     <tr>
     1026                        <td class="left">Authorization</td>
     1027                        <td class="left"><a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a> of <a href="#Part7" id="rfc.xref.Part7.1"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1028                     </tr>
     1029                     <tr>
     1030                        <td class="left">Expect</td>
     1031                        <td class="left"><a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;10.3</a></td>
     1032                     </tr>
     1033                     <tr>
     1034                        <td class="left">From</td>
     1035                        <td class="left"><a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;10.4</a></td>
     1036                     </tr>
     1037                     <tr>
     1038                        <td class="left">Host</td>
     1039                        <td class="left"><a href="p1-messaging.html#header.host" title="Host">Section 5.4</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td>
     1040                     </tr>
     1041                     <tr>
     1042                        <td class="left">If-Match</td>
     1043                        <td class="left"><a href="p4-conditional.html#header.if-match" title="If-Match">Section 3.1</a> of <a href="#Part4" id="rfc.xref.Part4.1"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1044                     </tr>
     1045                     <tr>
     1046                        <td class="left">If-Modified-Since</td>
     1047                        <td class="left"><a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 3.3</a> of <a href="#Part4" id="rfc.xref.Part4.2"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1048                     </tr>
     1049                     <tr>
     1050                        <td class="left">If-None-Match</td>
     1051                        <td class="left"><a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 3.2</a> of <a href="#Part4" id="rfc.xref.Part4.3"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1052                     </tr>
     1053                     <tr>
     1054                        <td class="left">If-Range</td>
     1055                        <td class="left"><a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a> of <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
     1056                     </tr>
     1057                     <tr>
     1058                        <td class="left">If-Unmodified-Since</td>
     1059                        <td class="left"><a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 3.4</a> of <a href="#Part4" id="rfc.xref.Part4.4"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1060                     </tr>
     1061                     <tr>
     1062                        <td class="left">Max-Forwards</td>
     1063                        <td class="left"><a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;10.6</a></td>
     1064                     </tr>
     1065                     <tr>
     1066                        <td class="left">Proxy-Authorization</td>
     1067                        <td class="left"><a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a> of <a href="#Part7" id="rfc.xref.Part7.2"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1068                     </tr>
     1069                     <tr>
     1070                        <td class="left">Range</td>
     1071                        <td class="left"><a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.2"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
     1072                     </tr>
     1073                     <tr>
     1074                        <td class="left">Referer</td>
     1075                        <td class="left"><a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;10.7</a></td>
     1076                     </tr>
     1077                     <tr>
     1078                        <td class="left">TE</td>
     1079                        <td class="left"><a href="p1-messaging.html#header.te" title="TE">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a></td>
     1080                     </tr>
     1081                     <tr>
     1082                        <td class="left">User-Agent</td>
     1083                        <td class="left"><a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;10.10</a></td>
     1084                     </tr>
     1085                  </tbody>
     1086               </table>
     1087            </div>
     1088         </div>
     1089         <div id="response.header.fields">
     1090            <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a href="#response.header.fields">Response Header Fields</a></h2>
     1091            <p id="rfc.section.3.3.p.1">The response header fields allow the server to pass additional information about the response which cannot be placed in the
     1092               status-line. These header fields give information about the server and about further access to the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     1093            </p>
     1094            <div id="rfc.table.u.3">
     1095               <table class="tt full left" cellpadding="3" cellspacing="0">
     1096                  <thead>
     1097                     <tr>
     1098                        <th>Header Field Name</th>
     1099                        <th>Defined in...</th>
     1100                     </tr>
     1101                  </thead>
     1102                  <tbody>
     1103                     <tr>
     1104                        <td class="left">Accept-Ranges</td>
     1105                        <td class="left"><a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 5.1</a> of <a href="#Part5" id="rfc.xref.Part5.3"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
     1106                     </tr>
     1107                     <tr>
     1108                        <td class="left">Age</td>
     1109                        <td class="left"><a href="p6-cache.html#header.age" title="Age">Section 3.1</a> of <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td>
     1110                     </tr>
     1111                     <tr>
     1112                        <td class="left">Allow</td>
     1113                        <td class="left"><a href="#header.allow" id="rfc.xref.header.allow.2" title="Allow">Section&nbsp;10.1</a></td>
     1114                     </tr>
     1115                     <tr>
     1116                        <td class="left">Date</td>
     1117                        <td class="left"><a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section&nbsp;10.2</a></td>
     1118                     </tr>
     1119                     <tr>
     1120                        <td class="left">ETag</td>
     1121                        <td class="left"><a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a> of <a href="#Part4" id="rfc.xref.Part4.5"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1122                     </tr>
     1123                     <tr>
     1124                        <td class="left">Location</td>
     1125                        <td class="left"><a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;10.5</a></td>
     1126                     </tr>
     1127                     <tr>
     1128                        <td class="left">Proxy-Authenticate</td>
     1129                        <td class="left"><a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a> of <a href="#Part7" id="rfc.xref.Part7.3"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1130                     </tr>
     1131                     <tr>
     1132                        <td class="left">Retry-After</td>
     1133                        <td class="left"><a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;10.8</a></td>
     1134                     </tr>
     1135                     <tr>
     1136                        <td class="left">Server</td>
     1137                        <td class="left"><a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;10.9</a></td>
     1138                     </tr>
     1139                     <tr>
     1140                        <td class="left">Vary</td>
     1141                        <td class="left"><a href="p6-cache.html#header.vary" title="Vary">Section 3.5</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td>
     1142                     </tr>
     1143                     <tr>
     1144                        <td class="left">WWW-Authenticate</td>
     1145                        <td class="left"><a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a> of <a href="#Part7" id="rfc.xref.Part7.4"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1146                     </tr>
     1147                  </tbody>
     1148               </table>
     1149            </div>
     1150         </div>
    10581151      </div>
    1059       <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a id="response.header.fields" href="#response.header.fields">Response Header Fields</a></h2>
    1060       <p id="rfc.section.3.3.p.1">The response header fields allow the server to pass additional information about the response which cannot be placed in the
    1061          status-line. These header fields give information about the server and about further access to the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    1062       </p>
    1063       <div id="rfc.table.u.3">
    1064          <table class="tt full left" cellpadding="3" cellspacing="0">
    1065             <thead>
    1066                <tr>
    1067                   <th>Header Field Name</th>
    1068                   <th>Defined in...</th>
    1069                </tr>
    1070             </thead>
    1071             <tbody>
    1072                <tr>
    1073                   <td class="left">Accept-Ranges</td>
    1074                   <td class="left"><a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 5.1</a> of <a href="#Part5" id="rfc.xref.Part5.3"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
    1075                </tr>
    1076                <tr>
    1077                   <td class="left">Age</td>
    1078                   <td class="left"><a href="p6-cache.html#header.age" title="Age">Section 3.1</a> of <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td>
    1079                </tr>
    1080                <tr>
    1081                   <td class="left">Allow</td>
    1082                   <td class="left"><a href="#header.allow" id="rfc.xref.header.allow.2" title="Allow">Section&nbsp;10.1</a></td>
    1083                </tr>
    1084                <tr>
    1085                   <td class="left">Date</td>
    1086                   <td class="left"><a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section&nbsp;10.2</a></td>
    1087                </tr>
    1088                <tr>
    1089                   <td class="left">ETag</td>
    1090                   <td class="left"><a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a> of <a href="#Part4" id="rfc.xref.Part4.5"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1091                </tr>
    1092                <tr>
    1093                   <td class="left">Location</td>
    1094                   <td class="left"><a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;10.5</a></td>
    1095                </tr>
    1096                <tr>
    1097                   <td class="left">Proxy-Authenticate</td>
    1098                   <td class="left"><a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a> of <a href="#Part7" id="rfc.xref.Part7.3"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    1099                </tr>
    1100                <tr>
    1101                   <td class="left">Retry-After</td>
    1102                   <td class="left"><a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;10.8</a></td>
    1103                </tr>
    1104                <tr>
    1105                   <td class="left">Server</td>
    1106                   <td class="left"><a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;10.9</a></td>
    1107                </tr>
    1108                <tr>
    1109                   <td class="left">Vary</td>
    1110                   <td class="left"><a href="p6-cache.html#header.vary" title="Vary">Section 3.5</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a></td>
    1111                </tr>
    1112                <tr>
    1113                   <td class="left">WWW-Authenticate</td>
    1114                   <td class="left"><a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a> of <a href="#Part7" id="rfc.xref.Part7.4"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    1115                </tr>
    1116             </tbody>
    1117          </table>
    1118       </div>
    1119       <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a id="status.code.and.reason.phrase" href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h1>
    1120       <p id="rfc.section.4.p.1">The status-code element is a 3-digit integer result code of the attempt to understand and satisfy the request.</p>
    1121       <p id="rfc.section.4.p.2">The reason-phrase is intended to give a short textual description of the status-code and is intended for a human user. The
    1122          client does not need to examine or display the reason-phrase.
    1123       </p>
    1124       <div id="rfc.figure.u.5"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span>  <a href="#status.code.and.reason.phrase" class="smpl">status-code</a>    = 3<a href="#notation" class="smpl">DIGIT</a>
     1152      <div id="status.code.and.reason.phrase">
     1153         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h1>
     1154         <p id="rfc.section.4.p.1">The status-code element is a 3-digit integer result code of the attempt to understand and satisfy the request.</p>
     1155         <p id="rfc.section.4.p.2">The reason-phrase is intended to give a short textual description of the status-code and is intended for a human user. The
     1156            client does not need to examine or display the reason-phrase.
     1157         </p>
     1158         <div id="rfc.figure.u.5"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span>  <a href="#status.code.and.reason.phrase" class="smpl">status-code</a>    = 3<a href="#notation" class="smpl">DIGIT</a>
    11251159  <a href="#status.code.and.reason.phrase" class="smpl">reason-phrase</a>  = *( <a href="#notation" class="smpl">HTAB</a> / <a href="#notation" class="smpl">SP</a> / <a href="#notation" class="smpl">VCHAR</a> / <a href="#core.rules" class="smpl">obs-text</a> )
    11261160</pre><p id="rfc.section.4.p.4">HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes,
    1127          though such understanding is obviously desirable. However, applications <em class="bcp14">MUST</em> understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent
    1128          to the x00 status code of that class, with the exception that an unrecognized response <em class="bcp14">MUST NOT</em> be cached. For example, if an unrecognized status code of 431 is received by the client, it can safely assume that there was
    1129          something wrong with its request and treat the response as if it had received a 400 status code. In such cases, user agents <em class="bcp14">SHOULD</em> present to the user the representation enclosed with the response, since that representation is likely to include human-readable
    1130          information which will explain the unusual status.
    1131       </p>
    1132       <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a id="overview.of.status.codes" href="#overview.of.status.codes">Overview of Status Codes</a></h2>
    1133       <p id="rfc.section.4.1.p.1">The status codes listed below are defined in <a href="#status.codes" title="Status Code Definitions">Section&nbsp;7</a> of this specification, <a href="p4-conditional.html#status.code.definitions" title="Status Code Definitions">Section 4</a> of <a href="#Part4" id="rfc.xref.Part4.6"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p5-range.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, and <a href="p7-auth.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part7" id="rfc.xref.Part7.5"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>. The reason phrases listed here are only recommendations — they can be replaced by local equivalents without affecting the
    1134          protocol.
    1135       </p>
    1136       <div id="rfc.table.u.4">
    1137          <table class="tt full left" cellpadding="3" cellspacing="0">
    1138             <thead>
    1139                <tr>
    1140                   <th>status-code</th>
    1141                   <th>reason-phrase</th>
    1142                   <th>Defined in...</th>
    1143                </tr>
    1144             </thead>
    1145             <tbody>
    1146                <tr>
    1147                   <td class="left">100</td>
    1148                   <td class="left">Continue</td>
    1149                   <td class="left"><a href="#status.100" id="rfc.xref.status.100.1" title="100 Continue">Section&nbsp;7.1.1</a></td>
    1150                </tr>
    1151                <tr>
    1152                   <td class="left">101</td>
    1153                   <td class="left">Switching Protocols</td>
    1154                   <td class="left"><a href="#status.101" id="rfc.xref.status.101.1" title="101 Switching Protocols">Section&nbsp;7.1.2</a></td>
    1155                </tr>
    1156                <tr>
    1157                   <td class="left">200</td>
    1158                   <td class="left">OK</td>
    1159                   <td class="left"><a href="#status.200" id="rfc.xref.status.200.1" title="200 OK">Section&nbsp;7.2.1</a></td>
    1160                </tr>
    1161                <tr>
    1162                   <td class="left">201</td>
    1163                   <td class="left">Created</td>
    1164                   <td class="left"><a href="#status.201" id="rfc.xref.status.201.1" title="201 Created">Section&nbsp;7.2.2</a></td>
    1165                </tr>
    1166                <tr>
    1167                   <td class="left">202</td>
    1168                   <td class="left">Accepted</td>
    1169                   <td class="left"><a href="#status.202" id="rfc.xref.status.202.1" title="202 Accepted">Section&nbsp;7.2.3</a></td>
    1170                </tr>
    1171                <tr>
    1172                   <td class="left">203</td>
    1173                   <td class="left">Non-Authoritative Information</td>
    1174                   <td class="left"><a href="#status.203" id="rfc.xref.status.203.1" title="203 Non-Authoritative Information">Section&nbsp;7.2.4</a></td>
    1175                </tr>
    1176                <tr>
    1177                   <td class="left">204</td>
    1178                   <td class="left">No Content</td>
    1179                   <td class="left"><a href="#status.204" id="rfc.xref.status.204.1" title="204 No Content">Section&nbsp;7.2.5</a></td>
    1180                </tr>
    1181                <tr>
    1182                   <td class="left">205</td>
    1183                   <td class="left">Reset Content</td>
    1184                   <td class="left"><a href="#status.205" id="rfc.xref.status.205.1" title="205 Reset Content">Section&nbsp;7.2.6</a></td>
    1185                </tr>
    1186                <tr>
    1187                   <td class="left">206</td>
    1188                   <td class="left">Partial Content</td>
    1189                   <td id="status.206" class="left"><a href="p5-range.html#status.206" title="206 Partial Content">Section 3.1</a> of <a href="#Part5" id="rfc.xref.Part5.5"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
    1190                </tr>
    1191                <tr>
    1192                   <td class="left">300</td>
    1193                   <td class="left">Multiple Choices</td>
    1194                   <td class="left"><a href="#status.300" id="rfc.xref.status.300.1" title="300 Multiple Choices">Section&nbsp;7.3.1</a></td>
    1195                </tr>
    1196                <tr>
    1197                   <td class="left">301</td>
    1198                   <td class="left">Moved Permanently</td>
    1199                   <td class="left"><a href="#status.301" id="rfc.xref.status.301.1" title="301 Moved Permanently">Section&nbsp;7.3.2</a></td>
    1200                </tr>
    1201                <tr>
    1202                   <td class="left">302</td>
    1203                   <td class="left">Found</td>
    1204                   <td class="left"><a href="#status.302" id="rfc.xref.status.302.1" title="302 Found">Section&nbsp;7.3.3</a></td>
    1205                </tr>
    1206                <tr>
    1207                   <td class="left">303</td>
    1208                   <td class="left">See Other</td>
    1209                   <td class="left"><a href="#status.303" id="rfc.xref.status.303.1" title="303 See Other">Section&nbsp;7.3.4</a></td>
    1210                </tr>
    1211                <tr>
    1212                   <td class="left">304</td>
    1213                   <td class="left">Not Modified</td>
    1214                   <td id="status.304" class="left"><a href="p4-conditional.html#status.304" title="304 Not Modified">Section 4.1</a> of <a href="#Part4" id="rfc.xref.Part4.7"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1215                </tr>
    1216                <tr>
    1217                   <td class="left">305</td>
    1218                   <td class="left">Use Proxy</td>
    1219                   <td class="left"><a href="#status.305" id="rfc.xref.status.305.1" title="305 Use Proxy">Section&nbsp;7.3.5</a></td>
    1220                </tr>
    1221                <tr>
    1222                   <td class="left">307</td>
    1223                   <td class="left">Temporary Redirect</td>
    1224                   <td class="left"><a href="#status.307" id="rfc.xref.status.307.1" title="307 Temporary Redirect">Section&nbsp;7.3.7</a></td>
    1225                </tr>
    1226                <tr>
    1227                   <td class="left">400</td>
    1228                   <td class="left">Bad Request</td>
    1229                   <td class="left"><a href="#status.400" id="rfc.xref.status.400.1" title="400 Bad Request">Section&nbsp;7.4.1</a></td>
    1230                </tr>
    1231                <tr>
    1232                   <td class="left">401</td>
    1233                   <td class="left">Unauthorized</td>
    1234                   <td id="status.401" class="left"><a href="p7-auth.html#status.401" title="401 Unauthorized">Section 3.1</a> of <a href="#Part7" id="rfc.xref.Part7.6"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    1235                </tr>
    1236                <tr>
    1237                   <td class="left">402</td>
    1238                   <td class="left">Payment Required</td>
    1239                   <td class="left"><a href="#status.402" id="rfc.xref.status.402.1" title="402 Payment Required">Section&nbsp;7.4.2</a></td>
    1240                </tr>
    1241                <tr>
    1242                   <td class="left">403</td>
    1243                   <td class="left">Forbidden</td>
    1244                   <td class="left"><a href="#status.403" id="rfc.xref.status.403.1" title="403 Forbidden">Section&nbsp;7.4.3</a></td>
    1245                </tr>
    1246                <tr>
    1247                   <td class="left">404</td>
    1248                   <td class="left">Not Found</td>
    1249                   <td class="left"><a href="#status.404" id="rfc.xref.status.404.1" title="404 Not Found">Section&nbsp;7.4.4</a></td>
    1250                </tr>
    1251                <tr>
    1252                   <td class="left">405</td>
    1253                   <td class="left">Method Not Allowed</td>
    1254                   <td class="left"><a href="#status.405" id="rfc.xref.status.405.1" title="405 Method Not Allowed">Section&nbsp;7.4.5</a></td>
    1255                </tr>
    1256                <tr>
    1257                   <td class="left">406</td>
    1258                   <td class="left">Not Acceptable</td>
    1259                   <td class="left"><a href="#status.406" id="rfc.xref.status.406.1" title="406 Not Acceptable">Section&nbsp;7.4.6</a></td>
    1260                </tr>
    1261                <tr>
    1262                   <td class="left">407</td>
    1263                   <td class="left">Proxy Authentication Required</td>
    1264                   <td id="status.407" class="left"><a href="p7-auth.html#status.407" title="407 Proxy Authentication Required">Section 3.2</a> of <a href="#Part7" id="rfc.xref.Part7.7"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
    1265                </tr>
    1266                <tr>
    1267                   <td class="left">408</td>
    1268                   <td class="left">Request Time-out</td>
    1269                   <td class="left"><a href="#status.408" id="rfc.xref.status.408.1" title="408 Request Timeout">Section&nbsp;7.4.7</a></td>
    1270                </tr>
    1271                <tr>
    1272                   <td class="left">409</td>
    1273                   <td class="left">Conflict</td>
    1274                   <td class="left"><a href="#status.409" id="rfc.xref.status.409.1" title="409 Conflict">Section&nbsp;7.4.8</a></td>
    1275                </tr>
    1276                <tr>
    1277                   <td class="left">410</td>
    1278                   <td class="left">Gone</td>
    1279                   <td class="left"><a href="#status.410" id="rfc.xref.status.410.1" title="410 Gone">Section&nbsp;7.4.9</a></td>
    1280                </tr>
    1281                <tr>
    1282                   <td class="left">411</td>
    1283                   <td class="left">Length Required</td>
    1284                   <td class="left"><a href="#status.411" id="rfc.xref.status.411.1" title="411 Length Required">Section&nbsp;7.4.10</a></td>
    1285                </tr>
    1286                <tr>
    1287                   <td class="left">412</td>
    1288                   <td class="left">Precondition Failed</td>
    1289                   <td id="status.412" class="left"><a href="p4-conditional.html#status.412" title="412 Precondition Failed">Section 4.2</a> of <a href="#Part4" id="rfc.xref.Part4.8"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
    1290                </tr>
    1291                <tr>
    1292                   <td class="left">413</td>
    1293                   <td class="left">Request Representation Too Large</td>
    1294                   <td class="left"><a href="#status.413" id="rfc.xref.status.413.1" title="413 Request Representation Too Large">Section&nbsp;7.4.11</a></td>
    1295                </tr>
    1296                <tr>
    1297                   <td class="left">414</td>
    1298                   <td class="left">URI Too Long</td>
    1299                   <td class="left"><a href="#status.414" id="rfc.xref.status.414.1" title="414 URI Too Long">Section&nbsp;7.4.12</a></td>
    1300                </tr>
    1301                <tr>
    1302                   <td class="left">415</td>
    1303                   <td class="left">Unsupported Media Type</td>
    1304                   <td class="left"><a href="#status.415" id="rfc.xref.status.415.1" title="415 Unsupported Media Type">Section&nbsp;7.4.13</a></td>
    1305                </tr>
    1306                <tr>
    1307                   <td class="left">416</td>
    1308                   <td class="left">Requested range not satisfiable</td>
    1309                   <td id="status.416" class="left"><a href="p5-range.html#status.416" title="416 Requested Range Not Satisfiable">Section 3.2</a> of <a href="#Part5" id="rfc.xref.Part5.6"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
    1310                </tr>
    1311                <tr>
    1312                   <td class="left">417</td>
    1313                   <td class="left">Expectation Failed</td>
    1314                   <td class="left"><a href="#status.417" id="rfc.xref.status.417.1" title="417 Expectation Failed">Section&nbsp;7.4.14</a></td>
    1315                </tr>
    1316                <tr>
    1317                   <td class="left">426</td>
    1318                   <td class="left">Upgrade Required</td>
    1319                   <td class="left"><a href="#status.426" id="rfc.xref.status.426.1" title="426 Upgrade Required">Section&nbsp;7.4.15</a></td>
    1320                </tr>
    1321                <tr>
    1322                   <td class="left">500</td>
    1323                   <td class="left">Internal Server Error</td>
    1324                   <td class="left"><a href="#status.500" id="rfc.xref.status.500.1" title="500 Internal Server Error">Section&nbsp;7.5.1</a></td>
    1325                </tr>
    1326                <tr>
    1327                   <td class="left">501</td>
    1328                   <td class="left">Not Implemented</td>
    1329                   <td class="left"><a href="#status.501" id="rfc.xref.status.501.1" title="501 Not Implemented">Section&nbsp;7.5.2</a></td>
    1330                </tr>
    1331                <tr>
    1332                   <td class="left">502</td>
    1333                   <td class="left">Bad Gateway</td>
    1334                   <td class="left"><a href="#status.502" id="rfc.xref.status.502.1" title="502 Bad Gateway">Section&nbsp;7.5.3</a></td>
    1335                </tr>
    1336                <tr>
    1337                   <td class="left">503</td>
    1338                   <td class="left">Service Unavailable</td>
    1339                   <td class="left"><a href="#status.503" id="rfc.xref.status.503.1" title="503 Service Unavailable">Section&nbsp;7.5.4</a></td>
    1340                </tr>
    1341                <tr>
    1342                   <td class="left">504</td>
    1343                   <td class="left">Gateway Time-out</td>
    1344                   <td class="left"><a href="#status.504" id="rfc.xref.status.504.1" title="504 Gateway Timeout">Section&nbsp;7.5.5</a></td>
    1345                </tr>
    1346                <tr>
    1347                   <td class="left">505</td>
    1348                   <td class="left">HTTP Version not supported</td>
    1349                   <td class="left"><a href="#status.505" id="rfc.xref.status.505.1" title="505 HTTP Version Not Supported">Section&nbsp;7.5.6</a></td>
    1350                </tr>
    1351             </tbody>
    1352          </table>
     1161            though such understanding is obviously desirable. However, applications <em class="bcp14">MUST</em> understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent
     1162            to the x00 status code of that class, with the exception that an unrecognized response <em class="bcp14">MUST NOT</em> be cached. For example, if an unrecognized status code of 431 is received by the client, it can safely assume that there was
     1163            something wrong with its request and treat the response as if it had received a 400 status code. In such cases, user agents <em class="bcp14">SHOULD</em> present to the user the representation enclosed with the response, since that representation is likely to include human-readable
     1164            information which will explain the unusual status.
     1165         </p>
     1166         <div id="overview.of.status.codes">
     1167            <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a href="#overview.of.status.codes">Overview of Status Codes</a></h2>
     1168            <p id="rfc.section.4.1.p.1">The status codes listed below are defined in <a href="#status.codes" title="Status Code Definitions">Section&nbsp;7</a> of this specification, <a href="p4-conditional.html#status.code.definitions" title="Status Code Definitions">Section 4</a> of <a href="#Part4" id="rfc.xref.Part4.6"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p5-range.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, and <a href="p7-auth.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part7" id="rfc.xref.Part7.5"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>. The reason phrases listed here are only recommendations — they can be replaced by local equivalents without affecting the
     1169               protocol.
     1170            </p>
     1171            <div id="rfc.table.u.4">
     1172               <table class="tt full left" cellpadding="3" cellspacing="0">
     1173                  <thead>
     1174                     <tr>
     1175                        <th>status-code</th>
     1176                        <th>reason-phrase</th>
     1177                        <th>Defined in...</th>
     1178                     </tr>
     1179                  </thead>
     1180                  <tbody>
     1181                     <tr>
     1182                        <td class="left">100</td>
     1183                        <td class="left">Continue</td>
     1184                        <td class="left"><a href="#status.100" id="rfc.xref.status.100.1" title="100 Continue">Section&nbsp;7.1.1</a></td>
     1185                     </tr>
     1186                     <tr>
     1187                        <td class="left">101</td>
     1188                        <td class="left">Switching Protocols</td>
     1189                        <td class="left"><a href="#status.101" id="rfc.xref.status.101.1" title="101 Switching Protocols">Section&nbsp;7.1.2</a></td>
     1190                     </tr>
     1191                     <tr>
     1192                        <td class="left">200</td>
     1193                        <td class="left">OK</td>
     1194                        <td class="left"><a href="#status.200" id="rfc.xref.status.200.1" title="200 OK">Section&nbsp;7.2.1</a></td>
     1195                     </tr>
     1196                     <tr>
     1197                        <td class="left">201</td>
     1198                        <td class="left">Created</td>
     1199                        <td class="left"><a href="#status.201" id="rfc.xref.status.201.1" title="201 Created">Section&nbsp;7.2.2</a></td>
     1200                     </tr>
     1201                     <tr>
     1202                        <td class="left">202</td>
     1203                        <td class="left">Accepted</td>
     1204                        <td class="left"><a href="#status.202" id="rfc.xref.status.202.1" title="202 Accepted">Section&nbsp;7.2.3</a></td>
     1205                     </tr>
     1206                     <tr>
     1207                        <td class="left">203</td>
     1208                        <td class="left">Non-Authoritative Information</td>
     1209                        <td class="left"><a href="#status.203" id="rfc.xref.status.203.1" title="203 Non-Authoritative Information">Section&nbsp;7.2.4</a></td>
     1210                     </tr>
     1211                     <tr>
     1212                        <td class="left">204</td>
     1213                        <td class="left">No Content</td>
     1214                        <td class="left"><a href="#status.204" id="rfc.xref.status.204.1" title="204 No Content">Section&nbsp;7.2.5</a></td>
     1215                     </tr>
     1216                     <tr>
     1217                        <td class="left">205</td>
     1218                        <td class="left">Reset Content</td>
     1219                        <td class="left"><a href="#status.205" id="rfc.xref.status.205.1" title="205 Reset Content">Section&nbsp;7.2.6</a></td>
     1220                     </tr>
     1221                     <tr>
     1222                        <td class="left">206</td>
     1223                        <td class="left">Partial Content</td>
     1224                        <td id="status.206" class="left"><a href="p5-range.html#status.206" title="206 Partial Content">Section 3.1</a> of <a href="#Part5" id="rfc.xref.Part5.5"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
     1225                     </tr>
     1226                     <tr>
     1227                        <td class="left">300</td>
     1228                        <td class="left">Multiple Choices</td>
     1229                        <td class="left"><a href="#status.300" id="rfc.xref.status.300.1" title="300 Multiple Choices">Section&nbsp;7.3.1</a></td>
     1230                     </tr>
     1231                     <tr>
     1232                        <td class="left">301</td>
     1233                        <td class="left">Moved Permanently</td>
     1234                        <td class="left"><a href="#status.301" id="rfc.xref.status.301.1" title="301 Moved Permanently">Section&nbsp;7.3.2</a></td>
     1235                     </tr>
     1236                     <tr>
     1237                        <td class="left">302</td>
     1238                        <td class="left">Found</td>
     1239                        <td class="left"><a href="#status.302" id="rfc.xref.status.302.1" title="302 Found">Section&nbsp;7.3.3</a></td>
     1240                     </tr>
     1241                     <tr>
     1242                        <td class="left">303</td>
     1243                        <td class="left">See Other</td>
     1244                        <td class="left"><a href="#status.303" id="rfc.xref.status.303.1" title="303 See Other">Section&nbsp;7.3.4</a></td>
     1245                     </tr>
     1246                     <tr>
     1247                        <td class="left">304</td>
     1248                        <td class="left">Not Modified</td>
     1249                        <td id="status.304" class="left"><a href="p4-conditional.html#status.304" title="304 Not Modified">Section 4.1</a> of <a href="#Part4" id="rfc.xref.Part4.7"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1250                     </tr>
     1251                     <tr>
     1252                        <td class="left">305</td>
     1253                        <td class="left">Use Proxy</td>
     1254                        <td class="left"><a href="#status.305" id="rfc.xref.status.305.1" title="305 Use Proxy">Section&nbsp;7.3.5</a></td>
     1255                     </tr>
     1256                     <tr>
     1257                        <td class="left">307</td>
     1258                        <td class="left">Temporary Redirect</td>
     1259                        <td class="left"><a href="#status.307" id="rfc.xref.status.307.1" title="307 Temporary Redirect">Section&nbsp;7.3.7</a></td>
     1260                     </tr>
     1261                     <tr>
     1262                        <td class="left">400</td>
     1263                        <td class="left">Bad Request</td>
     1264                        <td class="left"><a href="#status.400" id="rfc.xref.status.400.1" title="400 Bad Request">Section&nbsp;7.4.1</a></td>
     1265                     </tr>
     1266                     <tr>
     1267                        <td class="left">401</td>
     1268                        <td class="left">Unauthorized</td>
     1269                        <td id="status.401" class="left"><a href="p7-auth.html#status.401" title="401 Unauthorized">Section 3.1</a> of <a href="#Part7" id="rfc.xref.Part7.6"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1270                     </tr>
     1271                     <tr>
     1272                        <td class="left">402</td>
     1273                        <td class="left">Payment Required</td>
     1274                        <td class="left"><a href="#status.402" id="rfc.xref.status.402.1" title="402 Payment Required">Section&nbsp;7.4.2</a></td>
     1275                     </tr>
     1276                     <tr>
     1277                        <td class="left">403</td>
     1278                        <td class="left">Forbidden</td>
     1279                        <td class="left"><a href="#status.403" id="rfc.xref.status.403.1" title="403 Forbidden">Section&nbsp;7.4.3</a></td>
     1280                     </tr>
     1281                     <tr>
     1282                        <td class="left">404</td>
     1283                        <td class="left">Not Found</td>
     1284                        <td class="left"><a href="#status.404" id="rfc.xref.status.404.1" title="404 Not Found">Section&nbsp;7.4.4</a></td>
     1285                     </tr>
     1286                     <tr>
     1287                        <td class="left">405</td>
     1288                        <td class="left">Method Not Allowed</td>
     1289                        <td class="left"><a href="#status.405" id="rfc.xref.status.405.1" title="405 Method Not Allowed">Section&nbsp;7.4.5</a></td>
     1290                     </tr>
     1291                     <tr>
     1292                        <td class="left">406</td>
     1293                        <td class="left">Not Acceptable</td>
     1294                        <td class="left"><a href="#status.406" id="rfc.xref.status.406.1" title="406 Not Acceptable">Section&nbsp;7.4.6</a></td>
     1295                     </tr>
     1296                     <tr>
     1297                        <td class="left">407</td>
     1298                        <td class="left">Proxy Authentication Required</td>
     1299                        <td id="status.407" class="left"><a href="p7-auth.html#status.407" title="407 Proxy Authentication Required">Section 3.2</a> of <a href="#Part7" id="rfc.xref.Part7.7"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a></td>
     1300                     </tr>
     1301                     <tr>
     1302                        <td class="left">408</td>
     1303                        <td class="left">Request Time-out</td>
     1304                        <td class="left"><a href="#status.408" id="rfc.xref.status.408.1" title="408 Request Timeout">Section&nbsp;7.4.7</a></td>
     1305                     </tr>
     1306                     <tr>
     1307                        <td class="left">409</td>
     1308                        <td class="left">Conflict</td>
     1309                        <td class="left"><a href="#status.409" id="rfc.xref.status.409.1" title="409 Conflict">Section&nbsp;7.4.8</a></td>
     1310                     </tr>
     1311                     <tr>
     1312                        <td class="left">410</td>
     1313                        <td class="left">Gone</td>
     1314                        <td class="left"><a href="#status.410" id="rfc.xref.status.410.1" title="410 Gone">Section&nbsp;7.4.9</a></td>
     1315                     </tr>
     1316                     <tr>
     1317                        <td class="left">411</td>
     1318                        <td class="left">Length Required</td>
     1319                        <td class="left"><a href="#status.411" id="rfc.xref.status.411.1" title="411 Length Required">Section&nbsp;7.4.10</a></td>
     1320                     </tr>
     1321                     <tr>
     1322                        <td class="left">412</td>
     1323                        <td class="left">Precondition Failed</td>
     1324                        <td id="status.412" class="left"><a href="p4-conditional.html#status.412" title="412 Precondition Failed">Section 4.2</a> of <a href="#Part4" id="rfc.xref.Part4.8"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a></td>
     1325                     </tr>
     1326                     <tr>
     1327                        <td class="left">413</td>
     1328                        <td class="left">Request Representation Too Large</td>
     1329                        <td class="left"><a href="#status.413" id="rfc.xref.status.413.1" title="413 Request Representation Too Large">Section&nbsp;7.4.11</a></td>
     1330                     </tr>
     1331                     <tr>
     1332                        <td class="left">414</td>
     1333                        <td class="left">URI Too Long</td>
     1334                        <td class="left"><a href="#status.414" id="rfc.xref.status.414.1" title="414 URI Too Long">Section&nbsp;7.4.12</a></td>
     1335                     </tr>
     1336                     <tr>
     1337                        <td class="left">415</td>
     1338                        <td class="left">Unsupported Media Type</td>
     1339                        <td class="left"><a href="#status.415" id="rfc.xref.status.415.1" title="415 Unsupported Media Type">Section&nbsp;7.4.13</a></td>
     1340                     </tr>
     1341                     <tr>
     1342                        <td class="left">416</td>
     1343                        <td class="left">Requested range not satisfiable</td>
     1344                        <td id="status.416" class="left"><a href="p5-range.html#status.416" title="416 Requested Range Not Satisfiable">Section 3.2</a> of <a href="#Part5" id="rfc.xref.Part5.6"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a></td>
     1345                     </tr>
     1346                     <tr>
     1347                        <td class="left">417</td>
     1348                        <td class="left">Expectation Failed</td>
     1349                        <td class="left"><a href="#status.417" id="rfc.xref.status.417.1" title="417 Expectation Failed">Section&nbsp;7.4.14</a></td>
     1350                     </tr>
     1351                     <tr>
     1352                        <td class="left">426</td>
     1353                        <td class="left">Upgrade Required</td>
     1354                        <td class="left"><a href="#status.426" id="rfc.xref.status.426.1" title="426 Upgrade Required">Section&nbsp;7.4.15</a></td>
     1355                     </tr>
     1356                     <tr>
     1357                        <td class="left">500</td>
     1358                        <td class="left">Internal Server Error</td>
     1359                        <td class="left"><a href="#status.500" id="rfc.xref.status.500.1" title="500 Internal Server Error">Section&nbsp;7.5.1</a></td>
     1360                     </tr>
     1361                     <tr>
     1362                        <td class="left">501</td>
     1363                        <td class="left">Not Implemented</td>
     1364                        <td class="left"><a href="#status.501" id="rfc.xref.status.501.1" title="501 Not Implemented">Section&nbsp;7.5.2</a></td>
     1365                     </tr>
     1366                     <tr>
     1367                        <td class="left">502</td>
     1368                        <td class="left">Bad Gateway</td>
     1369                        <td class="left"><a href="#status.502" id="rfc.xref.status.502.1" title="502 Bad Gateway">Section&nbsp;7.5.3</a></td>
     1370                     </tr>
     1371                     <tr>
     1372                        <td class="left">503</td>
     1373                        <td class="left">Service Unavailable</td>
     1374                        <td class="left"><a href="#status.503" id="rfc.xref.status.503.1" title="503 Service Unavailable">Section&nbsp;7.5.4</a></td>
     1375                     </tr>
     1376                     <tr>
     1377                        <td class="left">504</td>
     1378                        <td class="left">Gateway Time-out</td>
     1379                        <td class="left"><a href="#status.504" id="rfc.xref.status.504.1" title="504 Gateway Timeout">Section&nbsp;7.5.5</a></td>
     1380                     </tr>
     1381                     <tr>
     1382                        <td class="left">505</td>
     1383                        <td class="left">HTTP Version not supported</td>
     1384                        <td class="left"><a href="#status.505" id="rfc.xref.status.505.1" title="505 HTTP Version Not Supported">Section&nbsp;7.5.6</a></td>
     1385                     </tr>
     1386                  </tbody>
     1387               </table>
     1388            </div>
     1389            <p id="rfc.section.4.1.p.2">Note that this list is not exhaustive — it does not include extension status codes defined in other specifications.</p>
     1390         </div>
     1391         <div id="status.code.registry">
     1392            <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a href="#status.code.registry">Status Code Registry</a></h2>
     1393            <p id="rfc.section.4.2.p.1">The HTTP Status Code Registry defines the name space for the status-code token in the status-line of an HTTP response.</p>
     1394            <p id="rfc.section.4.2.p.2">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.2"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="https://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
     1395            </p>
     1396            <p id="rfc.section.4.2.p.3">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-status-codes">http://www.iana.org/assignments/http-status-codes</a>&gt;.
     1397            </p>
     1398            <div id="considerations.for.new.status.codes">
     1399               <h3 id="rfc.section.4.2.1"><a href="#rfc.section.4.2.1">4.2.1</a>&nbsp;<a href="#considerations.for.new.status.codes">Considerations for New Status Codes</a></h3>
     1400               <p id="rfc.section.4.2.1.p.1">When it is necessary to express new semantics for a HTTP response that aren't specific to a single application or media type,
     1401                  and currently defined status codes are inadequate, a new status code can be registered.
     1402               </p>
     1403               <p id="rfc.section.4.2.1.p.2">HTTP status codes are generic; that is, they are potentially applicable to any resource, not just one particular media type,
     1404                  "type" of resource, or application. As such, it is preferred that new HTTP status codes be registered in a document that isn't
     1405                  specific to a single application, so that this is clear.
     1406               </p>
     1407               <p id="rfc.section.4.2.1.p.3">Definitions of new HTTP status codes typically explain the request conditions that produce a response containing the status
     1408                  code (e.g., combinations of request headers and/or method(s)), along with any interactions with response headers (e.g., those
     1409                  that are required, those that modify the semantics of the response).
     1410               </p>
     1411               <p id="rfc.section.4.2.1.p.4">New HTTP status codes are required to fall under one of the categories defined in <a href="#status.codes" title="Status Code Definitions">Section&nbsp;7</a>. To allow existing parsers to properly handle them, new status codes cannot disallow a response body, although they can mandate
     1412                  a zero-length response body. They can require the presence of one or more particular HTTP response header(s).
     1413               </p>
     1414               <p id="rfc.section.4.2.1.p.5">Likewise, their definitions can specify that caches are allowed to use heuristics to determine their freshness (see <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>; by default, it is not allowed), and can define how to determine the resource which they carry a representation for (see <a href="#identifying.response.associated.with.representation" title="Identifying the Resource Associated with a Representation">Section&nbsp;5.1</a>; by default, it is anonymous).
     1415               </p>
     1416            </div>
     1417         </div>
    13531418      </div>
    1354       <p id="rfc.section.4.1.p.2">Note that this list is not exhaustive — it does not include extension status codes defined in other specifications.</p>
    1355       <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a id="status.code.registry" href="#status.code.registry">Status Code Registry</a></h2>
    1356       <p id="rfc.section.4.2.p.1">The HTTP Status Code Registry defines the name space for the status-code token in the status-line of an HTTP response.</p>
    1357       <p id="rfc.section.4.2.p.2">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.2"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="http://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
    1358       </p>
    1359       <p id="rfc.section.4.2.p.3">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-status-codes">http://www.iana.org/assignments/http-status-codes</a>&gt;.
    1360       </p>
    1361       <h3 id="rfc.section.4.2.1"><a href="#rfc.section.4.2.1">4.2.1</a>&nbsp;<a id="considerations.for.new.status.codes" href="#considerations.for.new.status.codes">Considerations for New Status Codes</a></h3>
    1362       <p id="rfc.section.4.2.1.p.1">When it is necessary to express new semantics for a HTTP response that aren't specific to a single application or media type,
    1363          and currently defined status codes are inadequate, a new status code can be registered.
    1364       </p>
    1365       <p id="rfc.section.4.2.1.p.2">HTTP status codes are generic; that is, they are potentially applicable to any resource, not just one particular media type,
    1366          "type" of resource, or application. As such, it is preferred that new HTTP status codes be registered in a document that isn't
    1367          specific to a single application, so that this is clear.
    1368       </p>
    1369       <p id="rfc.section.4.2.1.p.3">Definitions of new HTTP status codes typically explain the request conditions that produce a response containing the status
    1370          code (e.g., combinations of request headers and/or method(s)), along with any interactions with response headers (e.g., those
    1371          that are required, those that modify the semantics of the response).
    1372       </p>
    1373       <p id="rfc.section.4.2.1.p.4">New HTTP status codes are required to fall under one of the categories defined in <a href="#status.codes" title="Status Code Definitions">Section&nbsp;7</a>. To allow existing parsers to properly handle them, new status codes cannot disallow a response body, although they can mandate
    1374          a zero-length response body. They can require the presence of one or more particular HTTP response header(s).
    1375       </p>
    1376       <p id="rfc.section.4.2.1.p.5">Likewise, their definitions can specify that caches are allowed to use heuristics to determine their freshness (see <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>; by default, it is not allowed), and can define how to determine the resource which they carry a representation for (see <a href="#identifying.response.associated.with.representation" title="Identifying the Resource Associated with a Representation">Section&nbsp;5.1</a>; by default, it is anonymous).
    1377       </p>
    1378       <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="representation" href="#representation">Representation</a></h1>
    1379       <p id="rfc.section.5.p.1">Request and Response messages <em class="bcp14">MAY</em> transfer a representation if not otherwise restricted by the request method or response status code. A representation consists
    1380          of metadata (representation header fields) and data (representation body). When a complete or partial representation is enclosed
    1381          in an HTTP message, it is referred to as the payload of the message. HTTP representations are defined in <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
    1382       </p>
    1383       <p id="rfc.section.5.p.2">A representation body is only present in a message when a message body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.26"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The representation body is obtained from the message body by decoding any Transfer-Encoding that might have been applied
    1384          to ensure safe and proper transfer of the message.
    1385       </p>
    1386       <h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a id="identifying.response.associated.with.representation" href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></h2>
    1387       <p id="rfc.section.5.1.p.1">It is sometimes necessary to determine an identifier for the resource associated with a representation.</p>
    1388       <p id="rfc.section.5.1.p.2">An HTTP request representation, when present, is always associated with an anonymous (i.e., unidentified) resource.</p>
    1389       <p id="rfc.section.5.1.p.3">In the common case, an HTTP response is a representation of the target resource (see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). However, this is not always the case. To determine the URI of the resource a response is associated with, the following
    1390          rules are used (with the first applicable one being selected):
    1391       </p>
    1392       <ol>
    1393          <li>If the response status code is 200 or 203 and the request method was GET, the response payload is a representation of the
    1394             target resource.
    1395          </li>
    1396          <li>If the response status code is 204, 206, or 304 and the request method was GET or HEAD, the response payload is a partial
    1397             representation of the target resource.
    1398          </li>
    1399          <li>If the response has a Content-Location header field, and that URI is the same as the effective request URI, the response payload
    1400             is a representation of the target resource.
    1401          </li>
    1402          <li>If the response has a Content-Location header field, and that URI is not the same as the effective request URI, then the response
    1403             asserts that its payload is a representation of the resource identified by the Content-Location URI. However, such an assertion
    1404             cannot be trusted unless it can be verified by other means (not defined by HTTP).
    1405          </li>
    1406          <li>Otherwise, the response is a representation of an anonymous (i.e., unidentified) resource.</li>
    1407       </ol>
    1408       <p id="rfc.section.5.1.p.5"> <span class="comment" id="TODO-req-uri">[<a href="#TODO-req-uri" class="smpl">TODO-req-uri</a>: The comparison function is going to have to be defined somewhere, because we already need to compare URIs for things like
    1409             cache invalidation.]</span>
    1410       </p>
    1411       <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a id="method.definitions" href="#method.definitions">Method Definitions</a></h1>
    1412       <p id="rfc.section.6.p.1">The set of common request methods for HTTP/1.1 is defined below. Although this set can be expanded, additional methods cannot
    1413          be assumed to share the same semantics for separately extended clients and servers.
    1414       </p>
    1415       <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a id="safe.and.idempotent" href="#safe.and.idempotent">Safe and Idempotent Methods</a></h2>
    1416       <div id="rfc.iref.s.1"></div>
    1417       <h3 id="rfc.section.6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;<a id="safe.methods" href="#safe.methods">Safe Methods</a></h3>
    1418       <p id="rfc.section.6.1.1.p.1">Implementors need to be aware that the software represents the user in their interactions over the Internet, and need to allow
    1419          the user to be aware of any actions they take which might have an unexpected significance to themselves or others.
    1420       </p>
    1421       <p id="rfc.section.6.1.1.p.2">In particular, the convention has been established that the GET, HEAD, OPTIONS, and TRACE request methods <em class="bcp14">SHOULD NOT</em> have the significance of taking an action other than retrieval. These request methods ought to be considered "<dfn id="safe">safe</dfn>". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is
    1422          made aware of the fact that a possibly unsafe action is being requested.
    1423       </p>
    1424       <p id="rfc.section.6.1.1.p.3">Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request;
    1425          in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the
    1426          side-effects, so therefore cannot be held accountable for them.
    1427       </p>
    1428       <div id="rfc.iref.i.1"></div>
    1429       <h3 id="rfc.section.6.1.2"><a href="#rfc.section.6.1.2">6.1.2</a>&nbsp;<a id="idempotent.methods" href="#idempotent.methods">Idempotent Methods</a></h3>
    1430       <p id="rfc.section.6.1.2.p.1">Request methods can also have the property of "idempotence" in that, aside from error or expiration issues, the intended effect
    1431          of multiple identical requests is the same as for a single request. PUT, DELETE, and all safe request methods are idempotent.
    1432          It is important to note that idempotence refers only to changes requested by the client: a server is free to change its state
    1433          due to multiple requests for the purpose of tracking those requests, versioning of results, etc.
    1434       </p>
    1435       <h2 id="rfc.section.6.2"><a href="#rfc.section.6.2">6.2</a>&nbsp;<a id="OPTIONS" href="#OPTIONS">OPTIONS</a></h2>
    1436       <div id="rfc.iref.o.1"></div>
    1437       <div id="rfc.iref.m.1"></div>
    1438       <p id="rfc.section.6.2.p.1">The OPTIONS method requests information about the communication options available on the request/response chain identified
    1439          by the effective request URI. This method allows a client to determine the options and/or requirements associated with a resource,
    1440          or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
    1441       </p>
    1442       <p id="rfc.section.6.2.p.2">Responses to the OPTIONS method are not cacheable.</p>
    1443       <p id="rfc.section.6.2.p.3">If the OPTIONS request includes a message body (as indicated by the presence of Content-Length or Transfer-Encoding), then
    1444          the media type <em class="bcp14">MUST</em> be indicated by a Content-Type field. Although this specification does not define any use for such a body, future extensions
    1445          to HTTP might use the OPTIONS body to make more detailed queries on the server.
    1446       </p>
    1447       <p id="rfc.section.6.2.p.4">If the request-target (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.28"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is an asterisk ("*"), the OPTIONS request is intended to apply to the server in general rather than to a specific resource.
    1448          Since a server's communication options typically depend on the resource, the "*" request is only useful as a "ping" or "no-op"
    1449          type of method; it does nothing beyond allowing the client to test the capabilities of the server. For example, this can be
    1450          used to test a proxy for HTTP/1.1 conformance (or lack thereof).
    1451       </p>
    1452       <p id="rfc.section.6.2.p.5">If the request-target is not an asterisk, the OPTIONS request applies only to the options that are available when communicating
    1453          with that resource.
    1454       </p>
    1455       <p id="rfc.section.6.2.p.6">A 200 response <em class="bcp14">SHOULD</em> include any header fields that indicate optional features implemented by the server and applicable to that resource (e.g.,
    1456          Allow), possibly including extensions not defined by this specification. The response body, if any, <em class="bcp14">SHOULD</em> also include information about the communication options. The format for such a body is not defined by this specification,
    1457          but might be defined by future extensions to HTTP. Content negotiation <em class="bcp14">MAY</em> be used to select the appropriate response format. If no response body is included, the response <em class="bcp14">MUST</em> include a Content-Length field with a field-value of "0".
    1458       </p>
    1459       <p id="rfc.section.6.2.p.7">The Max-Forwards header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;10.6</a>). If no Max-Forwards field is present in the request, then the forwarded request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
    1460       </p>
    1461       <h2 id="rfc.section.6.3"><a href="#rfc.section.6.3">6.3</a>&nbsp;<a id="GET" href="#GET">GET</a></h2>
    1462       <div id="rfc.iref.g.5"></div>
    1463       <div id="rfc.iref.m.2"></div>
    1464       <p id="rfc.section.6.3.p.1">The GET method requests transfer of a current representation of the target resource.</p>
    1465       <p id="rfc.section.6.3.p.2">If the target resource is a data-producing process, it is the produced data which shall be returned as the representation
    1466          in the response and not the source text of the process, unless that text happens to be the output of the process.
    1467       </p>
    1468       <p id="rfc.section.6.3.p.3">The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since,
    1469          If-Match, If-None-Match, or If-Range header field. A conditional GET requests that the representation be transferred only
    1470          under the circumstances described by the conditional header field(s). The conditional GET request is intended to reduce unnecessary
    1471          network usage by allowing cached representations to be refreshed without requiring multiple requests or transferring data
    1472          already held by the client.
    1473       </p>
    1474       <p id="rfc.section.6.3.p.4">The semantics of the GET method change to a "partial GET" if the request message includes a Range header field. A partial
    1475          GET requests that only part of the representation be transferred, as described in <a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.7"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>. The partial GET request is intended to reduce unnecessary network usage by allowing partially-retrieved representations
    1476          to be completed without transferring data already held by the client.
    1477       </p>
    1478       <p id="rfc.section.6.3.p.5">Bodies on GET requests have no defined semantics. Note that sending a body on a GET request might cause some existing implementations
    1479          to reject the request.
    1480       </p>
    1481       <p id="rfc.section.6.3.p.6">The response to a GET request is cacheable and <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests (see <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    1482       </p>
    1483       <p id="rfc.section.6.3.p.7">See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;12.2</a> for security considerations when used for forms.
    1484       </p>
    1485       <h2 id="rfc.section.6.4"><a href="#rfc.section.6.4">6.4</a>&nbsp;<a id="HEAD" href="#HEAD">HEAD</a></h2>
    1486       <div id="rfc.iref.h.1"></div>
    1487       <div id="rfc.iref.m.3"></div>
    1488       <p id="rfc.section.6.4.p.1">The HEAD method is identical to GET except that the server <em class="bcp14">MUST NOT</em> return a message body in the response. The metadata contained in the HTTP header fields in response to a HEAD request <em class="bcp14">SHOULD</em> be identical to the information sent in response to a GET request. This method can be used for obtaining metadata about the
    1489          representation implied by the request without transferring the representation body. This method is often used for testing
    1490          hypertext links for validity, accessibility, and recent modification.
    1491       </p>
    1492       <p id="rfc.section.6.4.p.2">The response to a HEAD request is cacheable and <em class="bcp14">MAY</em> be used to satisfy a subsequent HEAD request. It also has potential side effects on previously stored responses to GET; see <a href="p6-cache.html#head.effects" title="Updating Caches with HEAD Responses">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>.
    1493       </p>
    1494       <p id="rfc.section.6.4.p.3">Bodies on HEAD requests have no defined semantics. Note that sending a body on a HEAD request might cause some existing implementations
    1495          to reject the request.
    1496       </p>
    1497       <div id="rfc.iref.p.1"></div>
    1498       <div id="rfc.iref.m.4"></div>
    1499       <h2 id="rfc.section.6.5"><a href="#rfc.section.6.5">6.5</a>&nbsp;<a id="POST" href="#POST">POST</a></h2>
    1500       <p id="rfc.section.6.5.p.1">The POST method requests that the origin server accept the representation enclosed in the request as data to be processed
    1501          by the target resource. POST is designed to allow a uniform method to cover the following functions:
    1502       </p>
    1503       <ul>
    1504          <li>Annotation of existing resources;</li>
    1505          <li>Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles;</li>
    1506          <li>Providing a block of data, such as the result of submitting a form, to a data-handling process;</li>
    1507          <li>Extending a database through an append operation.</li>
    1508       </ul>
    1509       <p id="rfc.section.6.5.p.2">The actual function performed by the POST method is determined by the server and is usually dependent on the effective request
    1510          URI.
    1511       </p>
    1512       <p id="rfc.section.6.5.p.3">The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either
    1513          200 (OK) or 204 (No Content) is the appropriate response status code, depending on whether or not the response includes a
    1514          representation that describes the result.
    1515       </p>
    1516       <p id="rfc.section.6.5.p.4">If a resource has been created on the origin server, the response <em class="bcp14">SHOULD</em> be 201 (Created) and contain a representation which describes the status of the request and refers to the new resource, and
    1517          a Location header field (see <a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;10.5</a>).
    1518       </p>
    1519       <p id="rfc.section.6.5.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests.
    1520       </p>
    1521       <p id="rfc.section.6.5.p.6">Note that POST caching is not widely implemented. However, the 303 (See Other) response can be used to direct the user agent
    1522          to retrieve a cacheable resource.
    1523       </p>
    1524       <div id="rfc.iref.p.2"></div>
    1525       <div id="rfc.iref.m.5"></div>
    1526       <h2 id="rfc.section.6.6"><a href="#rfc.section.6.6">6.6</a>&nbsp;<a id="PUT" href="#PUT">PUT</a></h2>
    1527       <p id="rfc.section.6.6.p.1">The PUT method requests that the state of the target resource be created or replaced with the state defined by the representation
    1528          enclosed in the request message payload. A successful PUT of a given representation would suggest that a subsequent GET on
    1529          that same target resource will result in an equivalent representation being returned in a 200 (OK) response. However, there
    1530          is no guarantee that such a state change will be observable, since the target resource might be acted upon by other user agents
    1531          in parallel, or might be subject to dynamic processing by the origin server, before any subsequent GET is received. A successful
    1532          response only implies that the user agent's intent was achieved at the time of its processing by the origin server.
    1533       </p>
    1534       <p id="rfc.section.6.6.p.2">If the target resource does not have a current representation and the PUT successfully creates one, then the origin server <em class="bcp14">MUST</em> inform the user agent by sending a 201 (Created) response. If the target resource does have a current representation and that
    1535          representation is successfully modified in accordance with the state of the enclosed representation, then either a 200 (OK)
    1536          or 204 (No Content) response <em class="bcp14">SHOULD</em> be sent to indicate successful completion of the request.
    1537       </p>
    1538       <p id="rfc.section.6.6.p.3">Unrecognized header fields <em class="bcp14">SHOULD</em> be ignored (i.e., not saved as part of the resource state).
    1539       </p>
    1540       <p id="rfc.section.6.6.p.4">An origin server <em class="bcp14">SHOULD</em> verify that the PUT representation is consistent with any constraints which the server has for the target resource that cannot
    1541          or will not be changed by the PUT. This is particularly important when the origin server uses internal configuration information
    1542          related to the URI in order to set the values for representation metadata on GET responses. When a PUT representation is inconsistent
    1543          with the target resource, the origin server <em class="bcp14">SHOULD</em> either make them consistent, by transforming the representation or changing the resource configuration, or respond with an
    1544          appropriate error message containing sufficient information to explain why the representation is unsuitable. The 409 (Conflict)
    1545          or 415 (Unsupported Media Type) status codes are suggested, with the latter being specific to constraints on Content-Type
    1546          values.
    1547       </p>
    1548       <p id="rfc.section.6.6.p.5">For example, if the target resource is configured to always have a Content-Type of "text/html" and the representation being
    1549          PUT has a Content-Type of "image/jpeg", then the origin server <em class="bcp14">SHOULD</em> do one of: (a) reconfigure the target resource to reflect the new media type; (b) transform the PUT representation to a format
    1550          consistent with that of the resource before saving it as the new resource state; or, (c) reject the request with a 415 response
    1551          indicating that the target resource is limited to "text/html", perhaps including a link to a different resource that would
    1552          be a suitable target for the new representation.
    1553       </p>
    1554       <p id="rfc.section.6.6.p.6">HTTP does not define exactly how a PUT method affects the state of an origin server beyond what can be expressed by the intent
    1555          of the user agent request and the semantics of the origin server response. It does not define what a resource might be, in
    1556          any sense of that word, beyond the interface provided via HTTP. It does not define how resource state is "stored", nor how
    1557          such storage might change as a result of a change in resource state, nor how the origin server translates resource state into
    1558          representations. Generally speaking, all implementation details behind the resource interface are intentionally hidden by
    1559          the server.
    1560       </p>
    1561       <p id="rfc.section.6.6.p.7">The fundamental difference between the POST and PUT methods is highlighted by the different intent for the target resource.
    1562          The target resource in a POST request is intended to handle the enclosed representation as a data-accepting process, such
    1563          as for a gateway to some other protocol or a document that accepts annotations. In contrast, the target resource in a PUT
    1564          request is intended to take the enclosed representation as a new or replacement value. Hence, the intent of PUT is idempotent
    1565          and visible to intermediaries, even though the exact effect is only known by the origin server.
    1566       </p>
    1567       <p id="rfc.section.6.6.p.8">Proper interpretation of a PUT request presumes that the user agent knows what target resource is desired. A service that
    1568          is intended to select a proper URI on behalf of the client, after receiving a state-changing request, <em class="bcp14">SHOULD</em> be implemented using the POST method rather than PUT. If the origin server will not make the requested PUT state change to
    1569          the target resource and instead wishes to have it applied to a different resource, such as when the resource has been moved
    1570          to a different URI, then the origin server <em class="bcp14">MUST</em> send a 301 (Moved Permanently) response; the user agent <em class="bcp14">MAY</em> then make its own decision regarding whether or not to redirect the request.
    1571       </p>
    1572       <p id="rfc.section.6.6.p.9">A PUT request applied to the target resource <em class="bcp14">MAY</em> have side-effects on other resources. For example, an article might have a URI for identifying "the current version" (a resource)
    1573          which is separate from the URIs identifying each particular version (different resources that at one point shared the same
    1574          state as the current version resource). A successful PUT request on "the current version" URI might therefore create a new
    1575          version resource in addition to changing the state of the target resource, and might also cause links to be added between
    1576          the related resources.
    1577       </p>
    1578       <p id="rfc.section.6.6.p.10">An origin server <em class="bcp14">SHOULD</em> reject any PUT request that contains a Content-Range header field, since it might be misinterpreted as partial content (or
    1579          might be partial content that is being mistakenly PUT as a full representation). Partial content updates are possible by targeting
    1580          a separately identified resource with state that overlaps a portion of the larger resource, or by using a different method
    1581          that has been specifically defined for partial updates (for example, the PATCH method defined in <a href="#RFC5789" id="rfc.xref.RFC5789.1"><cite title="PATCH Method for HTTP">[RFC5789]</cite></a>).
    1582       </p>
    1583       <p id="rfc.section.6.6.p.11">Responses to the PUT method are not cacheable. If a PUT request passes through a cache that has one or more stored responses
    1584          for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.6</a> of <a href="#Part6" id="rfc.xref.Part6.9"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    1585       </p>
    1586       <div id="rfc.iref.d.1"></div>
    1587       <div id="rfc.iref.m.6"></div>
    1588       <h2 id="rfc.section.6.7"><a href="#rfc.section.6.7">6.7</a>&nbsp;<a id="DELETE" href="#DELETE">DELETE</a></h2>
    1589       <p id="rfc.section.6.7.p.1">The DELETE method requests that the origin server delete the target resource. This method <em class="bcp14">MAY</em> be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation
    1590          has been carried out, even if the status code returned from the origin server indicates that the action has been completed
    1591          successfully. However, the server <em class="bcp14">SHOULD NOT</em> indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible
    1592          location.
    1593       </p>
    1594       <p id="rfc.section.6.7.p.2">A successful response <em class="bcp14">SHOULD</em> be 200 (OK) if the response includes an representation describing the status, 202 (Accepted) if the action has not yet been
    1595          enacted, or 204 (No Content) if the action has been enacted but the response does not include a representation.
    1596       </p>
    1597       <p id="rfc.section.6.7.p.3">Bodies on DELETE requests have no defined semantics. Note that sending a body on a DELETE request might cause some existing
    1598          implementations to reject the request.
    1599       </p>
    1600       <p id="rfc.section.6.7.p.4">Responses to the DELETE method are not cacheable. If a DELETE request passes through a cache that has one or more stored responses
    1601          for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.6</a> of <a href="#Part6" id="rfc.xref.Part6.10"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    1602       </p>
    1603       <h2 id="rfc.section.6.8"><a href="#rfc.section.6.8">6.8</a>&nbsp;<a id="TRACE" href="#TRACE">TRACE</a></h2>
    1604       <div id="rfc.iref.t.1"></div>
    1605       <div id="rfc.iref.m.7"></div>
    1606       <p id="rfc.section.6.8.p.1">The TRACE method requests a remote, application-layer loop-back of the request message. The final recipient of the request <em class="bcp14">SHOULD</em> reflect the message received back to the client as the message body of a 200 (OK) response. The final recipient is either
    1607          the origin server or the first proxy to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.3" title="Max-Forwards">Section&nbsp;10.6</a>). A TRACE request <em class="bcp14">MUST NOT</em> include a message body.
    1608       </p>
    1609       <p id="rfc.section.6.8.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing
    1610          or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.29"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the
    1611          client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an
    1612          infinite loop.
    1613       </p>
    1614       <p id="rfc.section.6.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> have a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 7.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.30"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and contain a message body that encloses a copy of the entire request message. Responses to the TRACE method are not cacheable.
    1615       </p>
    1616       <div id="rfc.iref.c.1"></div>
    1617       <div id="rfc.iref.m.8"></div>
    1618       <h2 id="rfc.section.6.9"><a href="#rfc.section.6.9">6.9</a>&nbsp;<a id="CONNECT" href="#CONNECT">CONNECT</a></h2>
    1619       <p id="rfc.section.6.9.p.1">The CONNECT method requests that the proxy establish a tunnel to the request-target and, if successful, thereafter restrict
    1620          its behavior to blind forwarding of packets until the connection is closed.
    1621       </p>
    1622       <p id="rfc.section.6.9.p.2">When using CONNECT, the request-target <em class="bcp14">MUST</em> use the authority form (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.31"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>); i.e., the request-target consists of only the host name and port number of the tunnel destination, separated by a colon.
    1623          For example,
    1624       </p>
    1625       <div id="rfc.figure.u.6"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1
     1419      <div id="representation">
     1420         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a href="#representation">Representation</a></h1>
     1421         <p id="rfc.section.5.p.1">Request and Response messages <em class="bcp14">MAY</em> transfer a representation if not otherwise restricted by the request method or response status code. A representation consists
     1422            of metadata (representation header fields) and data (representation body). When a complete or partial representation is enclosed
     1423            in an HTTP message, it is referred to as the payload of the message. HTTP representations are defined in <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
     1424         </p>
     1425         <p id="rfc.section.5.p.2">A representation body is only present in a message when a message body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.26"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The representation body is obtained from the message body by decoding any Transfer-Encoding that might have been applied
     1426            to ensure safe and proper transfer of the message.
     1427         </p>
     1428         <div id="identifying.response.associated.with.representation">
     1429            <h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></h2>
     1430            <p id="rfc.section.5.1.p.1">It is sometimes necessary to determine an identifier for the resource associated with a representation.</p>
     1431            <p id="rfc.section.5.1.p.2">An HTTP request representation, when present, is always associated with an anonymous (i.e., unidentified) resource.</p>
     1432            <p id="rfc.section.5.1.p.3">In the common case, an HTTP response is a representation of the target resource (see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). However, this is not always the case. To determine the URI of the resource a response is associated with, the following
     1433               rules are used (with the first applicable one being selected):
     1434            </p>
     1435            <ol>
     1436               <li>If the response status code is 200 or 203 and the request method was GET, the response payload is a representation of the
     1437                  target resource.
     1438               </li>
     1439               <li>If the response status code is 204, 206, or 304 and the request method was GET or HEAD, the response payload is a partial
     1440                  representation of the target resource.
     1441               </li>
     1442               <li>If the response has a Content-Location header field, and that URI is the same as the effective request URI, the response payload
     1443                  is a representation of the target resource.
     1444               </li>
     1445               <li>If the response has a Content-Location header field, and that URI is not the same as the effective request URI, then the response
     1446                  asserts that its payload is a representation of the resource identified by the Content-Location URI. However, such an assertion
     1447                  cannot be trusted unless it can be verified by other means (not defined by HTTP).
     1448               </li>
     1449               <li>Otherwise, the response is a representation of an anonymous (i.e., unidentified) resource.</li>
     1450            </ol>
     1451            <p id="rfc.section.5.1.p.5"><span class="comment" id="TODO-req-uri">[<a href="#TODO-req-uri" class="smpl">TODO-req-uri</a>: The comparison function is going to have to be defined somewhere, because we already need to compare URIs for things like
     1452                  cache invalidation.]</span>
     1453            </p>
     1454         </div>
     1455      </div>
     1456      <div id="method.definitions">
     1457         <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a href="#method.definitions">Method Definitions</a></h1>
     1458         <p id="rfc.section.6.p.1">The set of common request methods for HTTP/1.1 is defined below. Although this set can be expanded, additional methods cannot
     1459            be assumed to share the same semantics for separately extended clients and servers.
     1460         </p>
     1461         <div id="safe.and.idempotent">
     1462            <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a></h2>
     1463            <div id="safe.methods">
     1464               <div id="rfc.iref.s.1"></div>
     1465               <h3 id="rfc.section.6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;<a href="#safe.methods">Safe Methods</a></h3>
     1466               <p id="rfc.section.6.1.1.p.1">Implementors need to be aware that the software represents the user in their interactions over the Internet, and need to allow
     1467                  the user to be aware of any actions they take which might have an unexpected significance to themselves or others.
     1468               </p>
     1469               <p id="rfc.section.6.1.1.p.2">In particular, the convention has been established that the GET, HEAD, OPTIONS, and TRACE request methods <em class="bcp14">SHOULD NOT</em> have the significance of taking an action other than retrieval. These request methods ought to be considered "<dfn id="safe">safe</dfn>". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is
     1470                  made aware of the fact that a possibly unsafe action is being requested.
     1471               </p>
     1472               <p id="rfc.section.6.1.1.p.3">Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request;
     1473                  in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the
     1474                  side-effects, so therefore cannot be held accountable for them.
     1475               </p>
     1476            </div>
     1477            <div id="idempotent.methods">
     1478               <div id="rfc.iref.i.1"></div>
     1479               <h3 id="rfc.section.6.1.2"><a href="#rfc.section.6.1.2">6.1.2</a>&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></h3>
     1480               <p id="rfc.section.6.1.2.p.1">Request methods can also have the property of "idempotence" in that, aside from error or expiration issues, the intended effect
     1481                  of multiple identical requests is the same as for a single request. PUT, DELETE, and all safe request methods are idempotent.
     1482                  It is important to note that idempotence refers only to changes requested by the client: a server is free to change its state
     1483                  due to multiple requests for the purpose of tracking those requests, versioning of results, etc.
     1484               </p>
     1485            </div>
     1486         </div>
     1487         <div id="OPTIONS">
     1488            <h2 id="rfc.section.6.2"><a href="#rfc.section.6.2">6.2</a>&nbsp;<a href="#OPTIONS">OPTIONS</a></h2>
     1489            <div id="rfc.iref.o.1"></div>
     1490            <div id="rfc.iref.m.1"></div>
     1491            <p id="rfc.section.6.2.p.1">The OPTIONS method requests information about the communication options available on the request/response chain identified
     1492               by the effective request URI. This method allows a client to determine the options and/or requirements associated with a resource,
     1493               or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
     1494            </p>
     1495            <p id="rfc.section.6.2.p.2">Responses to the OPTIONS method are not cacheable.</p>
     1496            <p id="rfc.section.6.2.p.3">If the OPTIONS request includes a message body (as indicated by the presence of Content-Length or Transfer-Encoding), then
     1497               the media type <em class="bcp14">MUST</em> be indicated by a Content-Type field. Although this specification does not define any use for such a body, future extensions
     1498               to HTTP might use the OPTIONS body to make more detailed queries on the server.
     1499            </p>
     1500            <p id="rfc.section.6.2.p.4">If the request-target (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.28"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is an asterisk ("*"), the OPTIONS request is intended to apply to the server in general rather than to a specific resource.
     1501               Since a server's communication options typically depend on the resource, the "*" request is only useful as a "ping" or "no-op"
     1502               type of method; it does nothing beyond allowing the client to test the capabilities of the server. For example, this can be
     1503               used to test a proxy for HTTP/1.1 conformance (or lack thereof).
     1504            </p>
     1505            <p id="rfc.section.6.2.p.5">If the request-target is not an asterisk, the OPTIONS request applies only to the options that are available when communicating
     1506               with that resource.
     1507            </p>
     1508            <p id="rfc.section.6.2.p.6">A 200 response <em class="bcp14">SHOULD</em> include any header fields that indicate optional features implemented by the server and applicable to that resource (e.g.,
     1509               Allow), possibly including extensions not defined by this specification. The response body, if any, <em class="bcp14">SHOULD</em> also include information about the communication options. The format for such a body is not defined by this specification,
     1510               but might be defined by future extensions to HTTP. Content negotiation <em class="bcp14">MAY</em> be used to select the appropriate response format. If no response body is included, the response <em class="bcp14">MUST</em> include a Content-Length field with a field-value of "0".
     1511            </p>
     1512            <p id="rfc.section.6.2.p.7">The Max-Forwards header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;10.6</a>). If no Max-Forwards field is present in the request, then the forwarded request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
     1513            </p>
     1514         </div>
     1515         <div id="GET">
     1516            <h2 id="rfc.section.6.3"><a href="#rfc.section.6.3">6.3</a>&nbsp;<a href="#GET">GET</a></h2>
     1517            <div id="rfc.iref.g.5"></div>
     1518            <div id="rfc.iref.m.2"></div>
     1519            <p id="rfc.section.6.3.p.1">The GET method requests transfer of a current representation of the target resource.</p>
     1520            <p id="rfc.section.6.3.p.2">If the target resource is a data-producing process, it is the produced data which shall be returned as the representation
     1521               in the response and not the source text of the process, unless that text happens to be the output of the process.
     1522            </p>
     1523            <p id="rfc.section.6.3.p.3">The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since,
     1524               If-Match, If-None-Match, or If-Range header field. A conditional GET requests that the representation be transferred only
     1525               under the circumstances described by the conditional header field(s). The conditional GET request is intended to reduce unnecessary
     1526               network usage by allowing cached representations to be refreshed without requiring multiple requests or transferring data
     1527               already held by the client.
     1528            </p>
     1529            <p id="rfc.section.6.3.p.4">The semantics of the GET method change to a "partial GET" if the request message includes a Range header field. A partial
     1530               GET requests that only part of the representation be transferred, as described in <a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.7"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>. The partial GET request is intended to reduce unnecessary network usage by allowing partially-retrieved representations
     1531               to be completed without transferring data already held by the client.
     1532            </p>
     1533            <p id="rfc.section.6.3.p.5">Bodies on GET requests have no defined semantics. Note that sending a body on a GET request might cause some existing implementations
     1534               to reject the request.
     1535            </p>
     1536            <p id="rfc.section.6.3.p.6">The response to a GET request is cacheable and <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests (see <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
     1537            </p>
     1538            <p id="rfc.section.6.3.p.7">See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;12.2</a> for security considerations when used for forms.
     1539            </p>
     1540         </div>
     1541         <div id="HEAD">
     1542            <h2 id="rfc.section.6.4"><a href="#rfc.section.6.4">6.4</a>&nbsp;<a href="#HEAD">HEAD</a></h2>
     1543            <div id="rfc.iref.h.1"></div>
     1544            <div id="rfc.iref.m.3"></div>
     1545            <p id="rfc.section.6.4.p.1">The HEAD method is identical to GET except that the server <em class="bcp14">MUST NOT</em> return a message body in the response. The metadata contained in the HTTP header fields in response to a HEAD request <em class="bcp14">SHOULD</em> be identical to the information sent in response to a GET request. This method can be used for obtaining metadata about the
     1546               representation implied by the request without transferring the representation body. This method is often used for testing
     1547               hypertext links for validity, accessibility, and recent modification.
     1548            </p>
     1549            <p id="rfc.section.6.4.p.2">The response to a HEAD request is cacheable and <em class="bcp14">MAY</em> be used to satisfy a subsequent HEAD request. It also has potential side effects on previously stored responses to GET; see <a href="p6-cache.html#head.effects" title="Updating Caches with HEAD Responses">Section 2.5</a> of <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>.
     1550            </p>
     1551            <p id="rfc.section.6.4.p.3">Bodies on HEAD requests have no defined semantics. Note that sending a body on a HEAD request might cause some existing implementations
     1552               to reject the request.
     1553            </p>
     1554         </div>
     1555         <div id="POST">
     1556            <div id="rfc.iref.p.1"></div>
     1557            <div id="rfc.iref.m.4"></div>
     1558            <h2 id="rfc.section.6.5"><a href="#rfc.section.6.5">6.5</a>&nbsp;<a href="#POST">POST</a></h2>
     1559            <p id="rfc.section.6.5.p.1">The POST method requests that the origin server accept the representation enclosed in the request as data to be processed
     1560               by the target resource. POST is designed to allow a uniform method to cover the following functions:
     1561            </p>
     1562            <ul>
     1563               <li>Annotation of existing resources;</li>
     1564               <li>Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles;</li>
     1565               <li>Providing a block of data, such as the result of submitting a form, to a data-handling process;</li>
     1566               <li>Extending a database through an append operation.</li>
     1567            </ul>
     1568            <p id="rfc.section.6.5.p.2">The actual function performed by the POST method is determined by the server and is usually dependent on the effective request
     1569               URI.
     1570            </p>
     1571            <p id="rfc.section.6.5.p.3">The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either
     1572               200 (OK) or 204 (No Content) is the appropriate response status code, depending on whether or not the response includes a
     1573               representation that describes the result.
     1574            </p>
     1575            <p id="rfc.section.6.5.p.4">If a resource has been created on the origin server, the response <em class="bcp14">SHOULD</em> be 201 (Created) and contain a representation which describes the status of the request and refers to the new resource, and
     1576               a Location header field (see <a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;10.5</a>).
     1577            </p>
     1578            <p id="rfc.section.6.5.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests.
     1579            </p>
     1580            <p id="rfc.section.6.5.p.6">Note that POST caching is not widely implemented. However, the 303 (See Other) response can be used to direct the user agent
     1581               to retrieve a cacheable resource.
     1582            </p>
     1583         </div>
     1584         <div id="PUT">
     1585            <div id="rfc.iref.p.2"></div>
     1586            <div id="rfc.iref.m.5"></div>
     1587            <h2 id="rfc.section.6.6"><a href="#rfc.section.6.6">6.6</a>&nbsp;<a href="#PUT">PUT</a></h2>
     1588            <p id="rfc.section.6.6.p.1">The PUT method requests that the state of the target resource be created or replaced with the state defined by the representation
     1589               enclosed in the request message payload. A successful PUT of a given representation would suggest that a subsequent GET on
     1590               that same target resource will result in an equivalent representation being returned in a 200 (OK) response. However, there
     1591               is no guarantee that such a state change will be observable, since the target resource might be acted upon by other user agents
     1592               in parallel, or might be subject to dynamic processing by the origin server, before any subsequent GET is received. A successful
     1593               response only implies that the user agent's intent was achieved at the time of its processing by the origin server.
     1594            </p>
     1595            <p id="rfc.section.6.6.p.2">If the target resource does not have a current representation and the PUT successfully creates one, then the origin server <em class="bcp14">MUST</em> inform the user agent by sending a 201 (Created) response. If the target resource does have a current representation and that
     1596               representation is successfully modified in accordance with the state of the enclosed representation, then either a 200 (OK)
     1597               or 204 (No Content) response <em class="bcp14">SHOULD</em> be sent to indicate successful completion of the request.
     1598            </p>
     1599            <p id="rfc.section.6.6.p.3">Unrecognized header fields <em class="bcp14">SHOULD</em> be ignored (i.e., not saved as part of the resource state).
     1600            </p>
     1601            <p id="rfc.section.6.6.p.4">An origin server <em class="bcp14">SHOULD</em> verify that the PUT representation is consistent with any constraints which the server has for the target resource that cannot
     1602               or will not be changed by the PUT. This is particularly important when the origin server uses internal configuration information
     1603               related to the URI in order to set the values for representation metadata on GET responses. When a PUT representation is inconsistent
     1604               with the target resource, the origin server <em class="bcp14">SHOULD</em> either make them consistent, by transforming the representation or changing the resource configuration, or respond with an
     1605               appropriate error message containing sufficient information to explain why the representation is unsuitable. The 409 (Conflict)
     1606               or 415 (Unsupported Media Type) status codes are suggested, with the latter being specific to constraints on Content-Type
     1607               values.
     1608            </p>
     1609            <p id="rfc.section.6.6.p.5">For example, if the target resource is configured to always have a Content-Type of "text/html" and the representation being
     1610               PUT has a Content-Type of "image/jpeg", then the origin server <em class="bcp14">SHOULD</em> do one of: (a) reconfigure the target resource to reflect the new media type; (b) transform the PUT representation to a format
     1611               consistent with that of the resource before saving it as the new resource state; or, (c) reject the request with a 415 response
     1612               indicating that the target resource is limited to "text/html", perhaps including a link to a different resource that would
     1613               be a suitable target for the new representation.
     1614            </p>
     1615            <p id="rfc.section.6.6.p.6">HTTP does not define exactly how a PUT method affects the state of an origin server beyond what can be expressed by the intent
     1616               of the user agent request and the semantics of the origin server response. It does not define what a resource might be, in
     1617               any sense of that word, beyond the interface provided via HTTP. It does not define how resource state is "stored", nor how
     1618               such storage might change as a result of a change in resource state, nor how the origin server translates resource state into
     1619               representations. Generally speaking, all implementation details behind the resource interface are intentionally hidden by
     1620               the server.
     1621            </p>
     1622            <p id="rfc.section.6.6.p.7">The fundamental difference between the POST and PUT methods is highlighted by the different intent for the target resource.
     1623               The target resource in a POST request is intended to handle the enclosed representation as a data-accepting process, such
     1624               as for a gateway to some other protocol or a document that accepts annotations. In contrast, the target resource in a PUT
     1625               request is intended to take the enclosed representation as a new or replacement value. Hence, the intent of PUT is idempotent
     1626               and visible to intermediaries, even though the exact effect is only known by the origin server.
     1627            </p>
     1628            <p id="rfc.section.6.6.p.8">Proper interpretation of a PUT request presumes that the user agent knows what target resource is desired. A service that
     1629               is intended to select a proper URI on behalf of the client, after receiving a state-changing request, <em class="bcp14">SHOULD</em> be implemented using the POST method rather than PUT. If the origin server will not make the requested PUT state change to
     1630               the target resource and instead wishes to have it applied to a different resource, such as when the resource has been moved
     1631               to a different URI, then the origin server <em class="bcp14">MUST</em> send a 301 (Moved Permanently) response; the user agent <em class="bcp14">MAY</em> then make its own decision regarding whether or not to redirect the request.
     1632            </p>
     1633            <p id="rfc.section.6.6.p.9">A PUT request applied to the target resource <em class="bcp14">MAY</em> have side-effects on other resources. For example, an article might have a URI for identifying "the current version" (a resource)
     1634               which is separate from the URIs identifying each particular version (different resources that at one point shared the same
     1635               state as the current version resource). A successful PUT request on "the current version" URI might therefore create a new
     1636               version resource in addition to changing the state of the target resource, and might also cause links to be added between
     1637               the related resources.
     1638            </p>
     1639            <p id="rfc.section.6.6.p.10">An origin server <em class="bcp14">SHOULD</em> reject any PUT request that contains a Content-Range header field, since it might be misinterpreted as partial content (or
     1640               might be partial content that is being mistakenly PUT as a full representation). Partial content updates are possible by targeting
     1641               a separately identified resource with state that overlaps a portion of the larger resource, or by using a different method
     1642               that has been specifically defined for partial updates (for example, the PATCH method defined in <a href="#RFC5789" id="rfc.xref.RFC5789.1"><cite title="PATCH Method for HTTP">[RFC5789]</cite></a>).
     1643            </p>
     1644            <p id="rfc.section.6.6.p.11">Responses to the PUT method are not cacheable. If a PUT request passes through a cache that has one or more stored responses
     1645               for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.6</a> of <a href="#Part6" id="rfc.xref.Part6.9"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
     1646            </p>
     1647         </div>
     1648         <div id="DELETE">
     1649            <div id="rfc.iref.d.1"></div>
     1650            <div id="rfc.iref.m.6"></div>
     1651            <h2 id="rfc.section.6.7"><a href="#rfc.section.6.7">6.7</a>&nbsp;<a href="#DELETE">DELETE</a></h2>
     1652            <p id="rfc.section.6.7.p.1">The DELETE method requests that the origin server delete the target resource. This method <em class="bcp14">MAY</em> be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation
     1653               has been carried out, even if the status code returned from the origin server indicates that the action has been completed
     1654               successfully. However, the server <em class="bcp14">SHOULD NOT</em> indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible
     1655               location.
     1656            </p>
     1657            <p id="rfc.section.6.7.p.2">A successful response <em class="bcp14">SHOULD</em> be 200 (OK) if the response includes an representation describing the status, 202 (Accepted) if the action has not yet been
     1658               enacted, or 204 (No Content) if the action has been enacted but the response does not include a representation.
     1659            </p>
     1660            <p id="rfc.section.6.7.p.3">Bodies on DELETE requests have no defined semantics. Note that sending a body on a DELETE request might cause some existing
     1661               implementations to reject the request.
     1662            </p>
     1663            <p id="rfc.section.6.7.p.4">Responses to the DELETE method are not cacheable. If a DELETE request passes through a cache that has one or more stored responses
     1664               for the effective request URI, those stored responses will be invalidated (see <a href="p6-cache.html#invalidation.after.updates.or.deletions" title="Request Methods that Invalidate">Section 2.6</a> of <a href="#Part6" id="rfc.xref.Part6.10"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
     1665            </p>
     1666         </div>
     1667         <div id="TRACE">
     1668            <h2 id="rfc.section.6.8"><a href="#rfc.section.6.8">6.8</a>&nbsp;<a href="#TRACE">TRACE</a></h2>
     1669            <div id="rfc.iref.t.1"></div>
     1670            <div id="rfc.iref.m.7"></div>
     1671            <p id="rfc.section.6.8.p.1">The TRACE method requests a remote, application-layer loop-back of the request message. The final recipient of the request <em class="bcp14">SHOULD</em> reflect the message received back to the client as the message body of a 200 (OK) response. The final recipient is either
     1672               the origin server or the first proxy to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.3" title="Max-Forwards">Section&nbsp;10.6</a>). A TRACE request <em class="bcp14">MUST NOT</em> include a message body.
     1673            </p>
     1674            <p id="rfc.section.6.8.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing
     1675               or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.29"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the
     1676               client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an
     1677               infinite loop.
     1678            </p>
     1679            <p id="rfc.section.6.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> have a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 7.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.30"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and contain a message body that encloses a copy of the entire request message. Responses to the TRACE method are not cacheable.
     1680            </p>
     1681         </div>
     1682         <div id="CONNECT">
     1683            <div id="rfc.iref.c.1"></div>
     1684            <div id="rfc.iref.m.8"></div>
     1685            <h2 id="rfc.section.6.9"><a href="#rfc.section.6.9">6.9</a>&nbsp;<a href="#CONNECT">CONNECT</a></h2>
     1686            <p id="rfc.section.6.9.p.1">The CONNECT method requests that the proxy establish a tunnel to the request-target and, if successful, thereafter restrict
     1687               its behavior to blind forwarding of packets until the connection is closed.
     1688            </p>
     1689            <p id="rfc.section.6.9.p.2">When using CONNECT, the request-target <em class="bcp14">MUST</em> use the authority form (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.31"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>); i.e., the request-target consists of only the host name and port number of the tunnel destination, separated by a colon.
     1690               For example,
     1691            </p>
     1692            <div id="rfc.figure.u.6"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1
    16261693Host: server.example.com:80
    16271694
    16281695</pre><p id="rfc.section.6.9.p.4">Any successful (2xx) response to a CONNECT request indicates that the proxy has established a connection to the requested
    1629          host and port, and has switched to tunneling the current connection to that server connection. The tunneled data from the
    1630          server begins immediately after the blank line that concludes the successful response's header block. A server <em class="bcp14">SHOULD NOT</em> send any Transfer-Encoding or Content-Length header fields in a successful response. A client <em class="bcp14">MUST</em> ignore any Content-Length or Transfer-Encoding header fields received in a successful response.
    1631       </p>
    1632       <p id="rfc.section.6.9.p.5">Any response other than a successful response indicates that the tunnel has not yet been formed and that the connection remains
    1633          governed by HTTP.
    1634       </p>
    1635       <p id="rfc.section.6.9.p.6">Proxy authentication might be used to establish the authority to create a tunnel:</p>
    1636       <div id="rfc.figure.u.7"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1
     1696               host and port, and has switched to tunneling the current connection to that server connection. The tunneled data from the
     1697               server begins immediately after the blank line that concludes the successful response's header block. A server <em class="bcp14">SHOULD NOT</em> send any Transfer-Encoding or Content-Length header fields in a successful response. A client <em class="bcp14">MUST</em> ignore any Content-Length or Transfer-Encoding header fields received in a successful response.
     1698            </p>
     1699            <p id="rfc.section.6.9.p.5">Any response other than a successful response indicates that the tunnel has not yet been formed and that the connection remains
     1700               governed by HTTP.
     1701            </p>
     1702            <p id="rfc.section.6.9.p.6">Proxy authentication might be used to establish the authority to create a tunnel:</p>
     1703            <div id="rfc.figure.u.7"></div><pre class="text2">CONNECT server.example.com:80 HTTP/1.1
    16371704Host: server.example.com:80
    16381705Proxy-Authorization: basic aGVsbG86d29ybGQ=
    16391706
    16401707</pre><p id="rfc.section.6.9.p.8">A message body on a CONNECT request has no defined semantics. Sending a body on a CONNECT request might cause existing implementations
    1641          to reject the request.
    1642       </p>
    1643       <p id="rfc.section.6.9.p.9">Similar to a pipelined HTTP/1.1 request, data to be tunneled from client to server <em class="bcp14">MAY</em> be sent immediately after the request (before a response is received). The usual caveats also apply: data may be discarded
    1644          if the eventual response is negative, and the connection may be reset with no response if more than one TCP segment is outstanding.
    1645       </p>
    1646       <p id="rfc.section.6.9.p.10">It may be the case that the proxy itself can only reach the requested origin server through another proxy. In this case, the
    1647          first proxy <em class="bcp14">SHOULD</em> make a CONNECT request of that next proxy, requesting a tunnel to the authority. A proxy <em class="bcp14">MUST NOT</em> respond with any 2xx status code unless it has either a direct or tunnel connection established to the authority.
    1648       </p>
    1649       <p id="rfc.section.6.9.p.11">If at any point either one of the peers gets disconnected, any outstanding data that came from that peer will be passed to
    1650          the other one, and after that also the other connection will be terminated by the proxy. If there is outstanding data to that
    1651          peer undelivered, that data will be discarded.
    1652       </p>
    1653       <p id="rfc.section.6.9.p.12">An origin server which receives a CONNECT request for itself <em class="bcp14">MAY</em> respond with a 2xx status code to indicate that a connection is established. However, most origin servers do not implement
    1654          CONNECT.
    1655       </p>
    1656       <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a id="status.codes" href="#status.codes">Status Code Definitions</a></h1>
    1657       <p id="rfc.section.7.p.1">The first digit of the status-code defines the class of response. The last two digits do not have any categorization role.
    1658          There are 5 values for the first digit:
    1659       </p>
    1660       <ul>
    1661          <li>1xx: Informational - Request received, continuing process</li>
    1662          <li>2xx: Success - The action was successfully received, understood, and accepted</li>
    1663          <li>3xx: Redirection - Further action must be taken in order to complete the request</li>
    1664          <li>4xx: Client Error - The request contains bad syntax or cannot be fulfilled</li>
    1665          <li>5xx: Server Error - The server failed to fulfill an apparently valid request</li>
    1666       </ul>
    1667       <p id="rfc.section.7.p.2">Each status-code is described below, including any metadata required in the response.</p>
    1668       <p id="rfc.section.7.p.3">For most status codes the response can carry a payload, in which case a Content-Type header field indicates the payload's
    1669          media type (<a href="p3-payload.html#header.content-type" title="Content-Type">Section 6.8</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
    1670       </p>
    1671       <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a id="status.1xx" href="#status.1xx">Informational 1xx</a></h2>
    1672       <p id="rfc.section.7.1.p.1">This class of status code indicates a provisional response, consisting only of the status-line and optional header fields,
    1673          and is terminated by an empty line. There are no required header fields for this class of status code. Since HTTP/1.0 did
    1674          not define any 1xx status codes, servers <em class="bcp14">MUST NOT</em> send a 1xx response to an HTTP/1.0 client except under experimental conditions.
    1675       </p>
    1676       <p id="rfc.section.7.1.p.2">A client <em class="bcp14">MUST</em> be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100
    1677          (Continue) status message. Unexpected 1xx status responses <em class="bcp14">MAY</em> be ignored by a user agent.
    1678       </p>
    1679       <p id="rfc.section.7.1.p.3">Proxies <em class="bcp14">MUST</em> forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself
    1680          requested the generation of the 1xx response. (For example, if a proxy adds a "Expect: 100-continue" field when it forwards
    1681          a request, then it need not forward the corresponding 100 (Continue) response(s).)
    1682       </p>
    1683       <div id="rfc.iref.22"></div>
    1684       <div id="rfc.iref.s.2"></div>
    1685       <h3 id="rfc.section.7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;<a id="status.100" href="#status.100">100 Continue</a></h3>
    1686       <p id="rfc.section.7.1.1.p.1">The client <em class="bcp14">SHOULD</em> continue with its request. This interim response is used to inform the client that the initial part of the request has been
    1687          received and has not yet been rejected by the server. The client <em class="bcp14">SHOULD</em> continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The
    1688          server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.32"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code.
    1689       </p>
    1690       <div id="rfc.iref.23"></div>
    1691       <div id="rfc.iref.s.3"></div>
    1692       <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a id="status.101" href="#status.101">101 Switching Protocols</a></h3>
    1693       <p id="rfc.section.7.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 6.5</a> of <a href="#Part1" id="rfc.xref.Part1.33"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined
    1694          by the response's Upgrade header field immediately after the empty line which terminates the 101 response.
    1695       </p>
    1696       <p id="rfc.section.7.1.2.p.2">The protocol <em class="bcp14">SHOULD</em> be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over
    1697          older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use
    1698          such features.
    1699       </p>
    1700       <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a id="status.2xx" href="#status.2xx">Successful 2xx</a></h2>
    1701       <p id="rfc.section.7.2.p.1">This class of status code indicates that the client's request was successfully received, understood, and accepted.</p>
    1702       <div id="rfc.iref.24"></div>
    1703       <div id="rfc.iref.s.4"></div>
    1704       <h3 id="rfc.section.7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;<a id="status.200" href="#status.200">200 OK</a></h3>
    1705       <p id="rfc.section.7.2.1.p.1">The request has succeeded. The payload returned with the response is dependent on the method used in the request, for example: </p>
    1706       <dl>
    1707          <dt>GET</dt>
    1708          <dd>a representation of the target resource is sent in the response;</dd>
    1709          <dt>HEAD</dt>
    1710          <dd>the same representation as GET, except without the message body;</dd>
    1711          <dt>POST</dt>
    1712          <dd>a representation describing or containing the result of the action;</dd>
    1713          <dt>TRACE</dt>
    1714          <dd>a representation containing the request message as received by the end server.</dd>
    1715       </dl>
    1716       <p id="rfc.section.7.2.1.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.11"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 200 responses.
    1717       </p>
    1718       <div id="rfc.iref.25"></div>
    1719       <div id="rfc.iref.s.5"></div>
    1720       <h3 id="rfc.section.7.2.2"><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;<a id="status.201" href="#status.201">201 Created</a></h3>
    1721       <p id="rfc.section.7.2.2.p.1">The request has been fulfilled and has resulted in a new resource being created.</p>
    1722       <p id="rfc.section.7.2.2.p.2">The newly created resource is typically linked to from the response payload, with the most relevant URI also being carried
    1723          in the Location header field. If the newly created resource's URI is the same as the Effective Request URI, this information
    1724          can be omitted (e.g., in the case of a response to a PUT request).
    1725       </p>
    1726       <p id="rfc.section.7.2.2.p.3">The origin server <em class="bcp14">MUST</em> create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server <em class="bcp14">SHOULD</em> respond with 202 (Accepted) response instead.
    1727       </p>
    1728       <p id="rfc.section.7.2.2.p.4">A 201 response <em class="bcp14">MAY</em> contain an ETag response header field indicating the current value of the entity-tag for the representation of the resource
    1729          just created (see <a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a> of <a href="#Part4" id="rfc.xref.Part4.9"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>).
    1730       </p>
    1731       <div id="rfc.iref.26"></div>
    1732       <div id="rfc.iref.s.6"></div>
    1733       <h3 id="rfc.section.7.2.3"><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;<a id="status.202" href="#status.202">202 Accepted</a></h3>
    1734       <p id="rfc.section.7.2.3.p.1">The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually
    1735          be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status
    1736          code from an asynchronous operation such as this.
    1737       </p>
    1738       <p id="rfc.section.7.2.3.p.2">The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process
    1739          (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the
    1740          server persist until the process is completed. The representation returned with this response <em class="bcp14">SHOULD</em> include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the
    1741          user can expect the request to be fulfilled.
    1742       </p>
    1743       <div id="rfc.iref.27"></div>
    1744       <div id="rfc.iref.s.7"></div>
    1745       <h3 id="rfc.section.7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;<a id="status.203" href="#status.203">203 Non-Authoritative Information</a></h3>
    1746       <p id="rfc.section.7.2.4.p.1">The representation in the response has been transformed or otherwise modified by a transforming proxy (<a href="p1-messaging.html#intermediaries" title="Intermediaries">Section 2.3</a> of <a href="#Part1" id="rfc.xref.Part1.34"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). Note that the behavior of transforming intermediaries is controlled by the no-transform Cache-Control directive (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 3.2</a> of <a href="#Part6" id="rfc.xref.Part6.12"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    1747       </p>
    1748       <p id="rfc.section.7.2.4.p.2">This status code is only appropriate when the response status code would have been 200 (OK) otherwise. When the status code
    1749          before transformation would have been different, the 214 Transformation Applied warn-code (<a href="p6-cache.html#header.warning" title="Warning">Section 3.6</a> of <a href="#Part6" id="rfc.xref.Part6.13"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) is appropriate.
    1750       </p>
    1751       <p id="rfc.section.7.2.4.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.14"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 203 responses.
    1752       </p>
    1753       <div id="rfc.iref.28"></div>
    1754       <div id="rfc.iref.s.8"></div>
    1755       <h3 id="rfc.section.7.2.5"><a href="#rfc.section.7.2.5">7.2.5</a>&nbsp;<a id="status.204" href="#status.204">204 No Content</a></h3>
    1756       <p id="rfc.section.7.2.5.p.1">The 204 (No Content) status code indicates that the server has successfully fulfilled the request and that there is no additional
    1757          content to return in the response payload body. Metadata in the response header fields refer to the target resource and its
    1758          current representation after the requested action.
    1759       </p>
    1760       <p id="rfc.section.7.2.5.p.2">For example, if a 204 status code is received in response to a PUT request and the response contains an ETag header field,
    1761          then the PUT was successful and the ETag field-value contains the entity-tag for the new representation of that target resource.
    1762       </p>
    1763       <p id="rfc.section.7.2.5.p.3">The 204 response allows a server to indicate that the action has been successfully applied to the target resource while implying
    1764          that the user agent <em class="bcp14">SHOULD NOT</em> traverse away from its current "document view" (if any). The server assumes that the user agent will provide some indication
    1765          of the success to its user, in accord with its own interface, and apply any new or updated metadata in the response to the
    1766          active representation.
    1767       </p>
    1768       <p id="rfc.section.7.2.5.p.4">For example, a 204 status code is commonly used with document editing interfaces corresponding to a "save" action, such that
    1769          the document being saved remains available to the user for editing. It is also frequently used with interfaces that expect
    1770          automated data transfers to be prevalent, such as within distributed version control systems.
    1771       </p>
    1772       <p id="rfc.section.7.2.5.p.5">The 204 response <em class="bcp14">MUST NOT</em> include a message body, and thus is always terminated by the first empty line after the header fields.
    1773       </p>
    1774       <div id="rfc.iref.29"></div>
    1775       <div id="rfc.iref.s.9"></div>
    1776       <h3 id="rfc.section.7.2.6"><a href="#rfc.section.7.2.6">7.2.6</a>&nbsp;<a id="status.205" href="#status.205">205 Reset Content</a></h3>
    1777       <p id="rfc.section.7.2.6.p.1">The server has fulfilled the request and the user agent <em class="bcp14">SHOULD</em> reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions
    1778          to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate
    1779          another input action.
    1780       </p>
    1781       <p id="rfc.section.7.2.6.p.2">The message body included with the response <em class="bcp14">MUST</em> be empty. Note that receivers still need to parse the response according to the algorithm defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.35"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>.
    1782       </p>
    1783       <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a>&nbsp;<a id="status.3xx" href="#status.3xx">Redirection 3xx</a></h2>
    1784       <p id="rfc.section.7.3.p.1">This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request.
    1785          If the required action involves a subsequent HTTP request, it <em class="bcp14">MAY</em> be carried out by the user agent without interaction with the user if and only if the method used in the second request is
    1786          known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>.
    1787       </p>
    1788       <p id="rfc.section.7.3.p.2">There are several types of redirects: </p>
    1789       <ol>
    1790          <li>
    1791             <p>Redirects of the request to another URI, either temporarily or permanently. The new URI is specified in the Location header
    1792                field. In this specification, the status codes 301 (Moved Permanently), 302 (Found), and 307 (Temporary Redirect) fall under
    1793                this category.
    1794             </p>
    1795          </li>
    1796          <li>
    1797             <p>Redirection to a new location that represents an indirect response to the request, such as the result of a POST operation
    1798                to be retrieved with a subsequent GET request. This is status code 303 (See Other).
    1799             </p>
    1800          </li>
    1801          <li>
    1802             <p>Redirection offering a choice of matching resources for use by agent-driven content negotiation (<a href="p3-payload.html#agent-driven.negotiation" title="Agent-driven Negotiation">Section 5.2</a> of <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). This is status code 300 (Multiple Choices).
    1803             </p>
    1804          </li>
    1805          <li>
    1806             <p>Other kinds of redirection, such as to a cached result (status code 304 (Not Modified), see <a href="p4-conditional.html#status.304" title="304 Not Modified">Section 4.1</a> of <a href="#Part4" id="rfc.xref.Part4.10"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>).
    1807             </p>
    1808          </li>
    1809       </ol>
    1810       <div class="note" id="rfc.section.7.3.p.3">
    1811          <p> <b>Note:</b> In HTTP/1.0, only the status codes 301 (Moved Permanently) and 302 (Found) were defined for the first type of redirect, and
    1812             the second type did not exist at all (<a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a>, <a href="http://tools.ietf.org/html/rfc1945#section-9.3">Section 9.3</a>). However it turned out that web forms using POST expected redirects to change the operation for the subsequent request to
    1813             retrieval (GET). To address this use case, HTTP/1.1 introduced the second type of redirect with the status code 303 (See Other)
    1814             (<a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="http://tools.ietf.org/html/rfc2068#section-10.3.4">Section 10.3.4</a>). As user agents did not change their behavior to maintain backwards compatibility, the first revision of HTTP/1.1 added
    1815             yet another status code, 307 (Temporary Redirect), for which the backwards compatibility problems did not apply (<a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="http://tools.ietf.org/html/rfc2616#section-10.3.8">Section 10.3.8</a>). Over 10 years later, most user agents still do method rewriting for status codes 301 and 302, therefore this specification
    1816             makes that behavior conformant in case the original request was POST.
    1817          </p>
     1708               to reject the request.
     1709            </p>
     1710            <p id="rfc.section.6.9.p.9">Similar to a pipelined HTTP/1.1 request, data to be tunneled from client to server <em class="bcp14">MAY</em> be sent immediately after the request (before a response is received). The usual caveats also apply: data may be discarded
     1711               if the eventual response is negative, and the connection may be reset with no response if more than one TCP segment is outstanding.
     1712            </p>
     1713            <p id="rfc.section.6.9.p.10">It may be the case that the proxy itself can only reach the requested origin server through another proxy. In this case, the
     1714               first proxy <em class="bcp14">SHOULD</em> make a CONNECT request of that next proxy, requesting a tunnel to the authority. A proxy <em class="bcp14">MUST NOT</em> respond with any 2xx status code unless it has either a direct or tunnel connection established to the authority.
     1715            </p>
     1716            <p id="rfc.section.6.9.p.11">If at any point either one of the peers gets disconnected, any outstanding data that came from that peer will be passed to
     1717               the other one, and after that also the other connection will be terminated by the proxy. If there is outstanding data to that
     1718               peer undelivered, that data will be discarded.
     1719            </p>
     1720            <p id="rfc.section.6.9.p.12">An origin server which receives a CONNECT request for itself <em class="bcp14">MAY</em> respond with a 2xx status code to indicate that a connection is established. However, most origin servers do not implement
     1721               CONNECT.
     1722            </p>
     1723         </div>
    18181724      </div>
    1819       <p id="rfc.section.7.3.p.4">A Location header field on a 3xx response indicates that a client <em class="bcp14">MAY</em> automatically redirect to the URI provided; see <a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;10.5</a>.
    1820       </p>
    1821       <p id="rfc.section.7.3.p.5">Note that for methods not known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>, automatic redirection needs to done with care, since the redirect might change the conditions under which the request was
    1822          issued.
    1823       </p>
    1824       <p id="rfc.section.7.3.p.6">Clients <em class="bcp14">SHOULD</em> detect and intervene in cyclical redirections (i.e., "infinite" redirection loops).
    1825       </p>
    1826       <div class="note" id="rfc.section.7.3.p.7">
    1827          <p> <b>Note:</b> An earlier version of this specification recommended a maximum of five redirections (<a href="#RFC2068" id="rfc.xref.RFC2068.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="http://tools.ietf.org/html/rfc2068#section-10.3">Section 10.3</a>). Content developers need to be aware that some clients might implement such a fixed limitation.
    1828          </p>
    1829       </div>
    1830       <div id="rfc.iref.30"></div>
    1831       <div id="rfc.iref.s.10"></div>
    1832       <h3 id="rfc.section.7.3.1"><a href="#rfc.section.7.3.1">7.3.1</a>&nbsp;<a id="status.300" href="#status.300">300 Multiple Choices</a></h3>
    1833       <p id="rfc.section.7.3.1.p.1">The target resource has more than one representation, each with its own specific location, and agent-driven negotiation information
    1834          (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) is being provided so that the user (or user agent) can select a preferred representation by redirecting its request to that
    1835          location.
    1836       </p>
    1837       <p id="rfc.section.7.3.1.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of representation metadata and location(s) from which the user or user agent can
    1838          choose the one most appropriate. Depending upon the format and the capabilities of the user agent, selection of the most appropriate
    1839          choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
    1840       </p>
    1841       <p id="rfc.section.7.3.1.p.3">If the server has a preferred choice of representation, it <em class="bcp14">SHOULD</em> include the specific URI for that representation in the Location field; user agents <em class="bcp14">MAY</em> use the Location field value for automatic redirection.
    1842       </p>
    1843       <p id="rfc.section.7.3.1.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.15"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 300 responses.
    1844       </p>
    1845       <div id="rfc.iref.31"></div>
    1846       <div id="rfc.iref.s.11"></div>
    1847       <h3 id="rfc.section.7.3.2"><a href="#rfc.section.7.3.2">7.3.2</a>&nbsp;<a id="status.301" href="#status.301">301 Moved Permanently</a></h3>
    1848       <p id="rfc.section.7.3.2.p.1">The target resource has been assigned a new permanent URI and any future references to this resource <em class="bcp14">SHOULD</em> use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the effective
    1849          request URI to one or more of the new references returned by the server, where possible.
    1850       </p>
    1851       <p id="rfc.section.7.3.2.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.16"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 301 responses.
    1852       </p>
    1853       <p id="rfc.section.7.3.2.p.3">The new permanent URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
    1854          the new URI(s).
    1855       </p>
    1856       <div class="note" id="rfc.section.7.3.2.p.4">
    1857          <p> <b>Note:</b> For historic reasons, user agents <em class="bcp14">MAY</em> change the request method from POST to GET for the subsequent request. If this behavior is undesired, status code 307 (Temporary
    1858             Redirect) can be used instead.
    1859          </p>
    1860       </div>
    1861       <div id="rfc.iref.32"></div>
    1862       <div id="rfc.iref.s.12"></div>
    1863       <h3 id="rfc.section.7.3.3"><a href="#rfc.section.7.3.3">7.3.3</a>&nbsp;<a id="status.302" href="#status.302">302 Found</a></h3>
    1864       <p id="rfc.section.7.3.3.p.1">The target resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
    1865       </p>
    1866       <p id="rfc.section.7.3.3.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
    1867          the new URI(s).
    1868       </p>
    1869       <div class="note" id="rfc.section.7.3.3.p.3">
    1870          <p> <b>Note:</b> For historic reasons, user agents <em class="bcp14">MAY</em> change the request method from POST to GET for the subsequent request. If this behavior is undesired, status code 307 (Temporary
    1871             Redirect) can be used instead.
    1872          </p>
    1873       </div>
    1874       <div id="rfc.iref.33"></div>
    1875       <div id="rfc.iref.s.13"></div>
    1876       <h3 id="rfc.section.7.3.4"><a href="#rfc.section.7.3.4">7.3.4</a>&nbsp;<a id="status.303" href="#status.303">303 See Other</a></h3>
    1877       <p id="rfc.section.7.3.4.p.1">The 303 status code indicates that the server is redirecting the user agent to a different resource, as indicated by a URI
    1878          in the Location header field, that is intended to provide an indirect response to the original request. In order to satisfy
    1879          the original request, a user agent <em class="bcp14">SHOULD</em> perform a retrieval request using the Location URI (a GET or HEAD request if using HTTP), which may itself be redirected further,
    1880          and present the eventual result as an answer to the original request. Note that the new URI in the Location header field is
    1881          not considered equivalent to the effective request URI.
    1882       </p>
    1883       <p id="rfc.section.7.3.4.p.2">This status code is generally applicable to any HTTP method. It is primarily used to allow the output of a POST action to
    1884          redirect the user agent to a selected resource, since doing so provides the information corresponding to the POST response
    1885          in a form that can be separately identified, bookmarked, and cached independent of the original request.
    1886       </p>
    1887       <p id="rfc.section.7.3.4.p.3">A 303 response to a GET request indicates that the requested resource does not have a representation of its own that can be
    1888          transferred by the server over HTTP. The Location URI indicates a resource that is descriptive of the target resource, such
    1889          that the follow-on representation might be useful to recipients without implying that it adequately represents the target
    1890          resource. Note that answers to the questions of what can be represented, what representations are adequate, and what might
    1891          be a useful description are outside the scope of HTTP and thus entirely determined by the URI owner(s).
    1892       </p>
    1893       <p id="rfc.section.7.3.4.p.4">Except for responses to a HEAD request, the representation of a 303 response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the Location URI.
    1894       </p>
    1895       <div id="rfc.iref.34"></div>
    1896       <div id="rfc.iref.s.14"></div>
    1897       <h3 id="rfc.section.7.3.5"><a href="#rfc.section.7.3.5">7.3.5</a>&nbsp;<a id="status.305" href="#status.305">305 Use Proxy</a></h3>
    1898       <p id="rfc.section.7.3.5.p.1">The 305 status code was defined in a previous version of this specification (see <a href="#changes.from.rfc.2616" title="Changes from RFC 2616">Appendix&nbsp;A</a>), and is now deprecated.
    1899       </p>
    1900       <div id="rfc.iref.35"></div>
    1901       <div id="rfc.iref.s.15"></div>
    1902       <h3 id="rfc.section.7.3.6"><a href="#rfc.section.7.3.6">7.3.6</a>&nbsp;<a id="status.306" href="#status.306">306 (Unused)</a></h3>
    1903       <p id="rfc.section.7.3.6.p.1">The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.</p>
    1904       <div id="rfc.iref.36"></div>
    1905       <div id="rfc.iref.s.16"></div>
    1906       <h3 id="rfc.section.7.3.7"><a href="#rfc.section.7.3.7">7.3.7</a>&nbsp;<a id="status.307" href="#status.307">307 Temporary Redirect</a></h3>
    1907       <p id="rfc.section.7.3.7.p.1">The target resource resides temporarily under a different URI. Since the redirection can change over time, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
    1908       </p>
    1909       <p id="rfc.section.7.3.7.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
    1910          the new URI(s).
    1911       </p>
    1912       <div class="note" id="rfc.section.7.3.7.p.3">
    1913          <p> <b>Note:</b> This status code is similar to 302 Found, except that it does not allow rewriting the request method from POST to GET. This
    1914             specification defines no equivalent counterpart for 301 Moved Permanently.
    1915          </p>
    1916       </div>
    1917       <h2 id="rfc.section.7.4"><a href="#rfc.section.7.4">7.4</a>&nbsp;<a id="status.4xx" href="#status.4xx">Client Error 4xx</a></h2>
    1918       <p id="rfc.section.7.4.p.1">The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD
    1919          request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
    1920          These status codes are applicable to any request method. User agents <em class="bcp14">SHOULD</em> display any included representation to the user.
    1921       </p>
    1922       <div id="rfc.iref.37"></div>
    1923       <div id="rfc.iref.s.17"></div>
    1924       <h3 id="rfc.section.7.4.1"><a href="#rfc.section.7.4.1">7.4.1</a>&nbsp;<a id="status.400" href="#status.400">400 Bad Request</a></h3>
    1925       <p id="rfc.section.7.4.1.p.1">The server cannot or will not process the request, due to a client error (e.g., malformed syntax).</p>
    1926       <div id="rfc.iref.38"></div>
    1927       <div id="rfc.iref.s.18"></div>
    1928       <h3 id="rfc.section.7.4.2"><a href="#rfc.section.7.4.2">7.4.2</a>&nbsp;<a id="status.402" href="#status.402">402 Payment Required</a></h3>
    1929       <p id="rfc.section.7.4.2.p.1">This code is reserved for future use.</p>
    1930       <div id="rfc.iref.39"></div>
    1931       <div id="rfc.iref.s.19"></div>
    1932       <h3 id="rfc.section.7.4.3"><a href="#rfc.section.7.4.3">7.4.3</a>&nbsp;<a id="status.403" href="#status.403">403 Forbidden</a></h3>
    1933       <p id="rfc.section.7.4.3.p.1">The server understood the request, but refuses to authorize it. Providing different user authentication credentials might
    1934          be successful, but any credentials that were provided in the request are insufficient. The request <em class="bcp14">SHOULD NOT</em> be repeated with the same credentials.
    1935       </p>
    1936       <p id="rfc.section.7.4.3.p.2">If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it <em class="bcp14">SHOULD</em> describe the reason for the refusal in the representation. If the server does not wish to make this information available
    1937          to the client, the status code 404 (Not Found) <em class="bcp14">MAY</em> be used instead.
    1938       </p>
    1939       <div id="rfc.iref.40"></div>
    1940       <div id="rfc.iref.s.20"></div>
    1941       <h3 id="rfc.section.7.4.4"><a href="#rfc.section.7.4.4">7.4.4</a>&nbsp;<a id="status.404" href="#status.404">404 Not Found</a></h3>
    1942       <p id="rfc.section.7.4.4.p.1">The server has not found anything matching the effective request URI. No indication is given of whether the condition is temporary
    1943          or permanent. The 410 (Gone) status code <em class="bcp14">SHOULD</em> be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable
    1944          and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request
    1945          has been refused, or when no other response is applicable.
    1946       </p>
    1947       <div id="rfc.iref.41"></div>
    1948       <div id="rfc.iref.s.21"></div>
    1949       <h3 id="rfc.section.7.4.5"><a href="#rfc.section.7.4.5">7.4.5</a>&nbsp;<a id="status.405" href="#status.405">405 Method Not Allowed</a></h3>
    1950       <p id="rfc.section.7.4.5.p.1">The method specified in the request-line is not allowed for the target resource. The response <em class="bcp14">MUST</em> include an Allow header field containing a list of valid methods for the requested resource.
    1951       </p>
    1952       <div id="rfc.iref.42"></div>
    1953       <div id="rfc.iref.s.22"></div>
    1954       <h3 id="rfc.section.7.4.6"><a href="#rfc.section.7.4.6">7.4.6</a>&nbsp;<a id="status.406" href="#status.406">406 Not Acceptable</a></h3>
    1955       <p id="rfc.section.7.4.6.p.1">The resource identified by the request is only capable of generating response representations which have content characteristics
    1956          not acceptable according to the Accept and Accept-* header fields sent in the request (see <a href="p3-payload.html#header.field.definitions" title="Header Field Definitions">Section 6</a> of <a href="#Part3" id="rfc.xref.Part3.12"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
    1957       </p>
    1958       <p id="rfc.section.7.4.6.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of available representation characteristics and location(s) from which the user
    1959          or user agent can choose the one most appropriate. Depending upon the format and the capabilities of the user agent, selection
    1960          of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
    1961       </p>
    1962       <div class="note" id="rfc.section.7.4.6.p.3">
    1963          <p> <b>Note:</b> HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept header fields sent in the
    1964             request. In some cases, this might even be preferable to sending a 406 response. User agents are encouraged to inspect the
    1965             header fields of an incoming response to determine if it is acceptable.
    1966          </p>
    1967       </div>
    1968       <p id="rfc.section.7.4.6.p.4">If the response could be unacceptable, a user agent <em class="bcp14">SHOULD</em> temporarily stop receipt of more data and query the user for a decision on further actions.
    1969       </p>
    1970       <div id="rfc.iref.43"></div>
    1971       <div id="rfc.iref.s.23"></div>
    1972       <h3 id="rfc.section.7.4.7"><a href="#rfc.section.7.4.7">7.4.7</a>&nbsp;<a id="status.408" href="#status.408">408 Request Timeout</a></h3>
    1973       <p id="rfc.section.7.4.7.p.1">The client did not produce a request within the time that the server was prepared to wait. The client <em class="bcp14">MAY</em> repeat the request without modifications at any later time.
    1974       </p>
    1975       <div id="rfc.iref.44"></div>
    1976       <div id="rfc.iref.s.24"></div>
    1977       <h3 id="rfc.section.7.4.8"><a href="#rfc.section.7.4.8">7.4.8</a>&nbsp;<a id="status.409" href="#status.409">409 Conflict</a></h3>
    1978       <p id="rfc.section.7.4.8.p.1">The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in
    1979          situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response
    1980          body <em class="bcp14">SHOULD</em> include enough information for the user to recognize the source of the conflict. Ideally, the response representation would
    1981          include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.
    1982       </p>
    1983       <p id="rfc.section.7.4.8.p.2">Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the representation
    1984          being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might
    1985          use the 409 response to indicate that it can't complete the request. In this case, the response representation would likely
    1986          contain a list of the differences between the two versions.
    1987       </p>
    1988       <div id="rfc.iref.45"></div>
    1989       <div id="rfc.iref.s.25"></div>
    1990       <h3 id="rfc.section.7.4.9"><a href="#rfc.section.7.4.9">7.4.9</a>&nbsp;<a id="status.410" href="#status.410">410 Gone</a></h3>
    1991       <p id="rfc.section.7.4.9.p.1">The target resource is no longer available at the server and no forwarding address is known. This condition is expected to
    1992          be considered permanent. Clients with link editing capabilities <em class="bcp14">SHOULD</em> delete references to the effective request URI after user approval. If the server does not know, or has no facility to determine,
    1993          whether or not the condition is permanent, the status code 404 (Not Found) <em class="bcp14">SHOULD</em> be used instead.
    1994       </p>
    1995       <p id="rfc.section.7.4.9.p.2">The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource
    1996          is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event
    1997          is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's
    1998          site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time
    1999          — that is left to the discretion of the server owner.
    2000       </p>
    2001       <p id="rfc.section.7.4.9.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.17"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 410 responses.
    2002       </p>
    2003       <div id="rfc.iref.46"></div>
    2004       <div id="rfc.iref.s.26"></div>
    2005       <h3 id="rfc.section.7.4.10"><a href="#rfc.section.7.4.10">7.4.10</a>&nbsp;<a id="status.411" href="#status.411">411 Length Required</a></h3>
    2006       <p id="rfc.section.7.4.10.p.1">The server refuses to accept the request without a defined Content-Length. The client <em class="bcp14">MAY</em> repeat the request if it adds a valid Content-Length header field containing the length of the message body in the request
    2007          message.
    2008       </p>
    2009       <div id="rfc.iref.47"></div>
    2010       <div id="rfc.iref.s.27"></div>
    2011       <h3 id="rfc.section.7.4.11"><a href="#rfc.section.7.4.11">7.4.11</a>&nbsp;<a id="status.413" href="#status.413">413 Request Representation Too Large</a></h3>
    2012       <p id="rfc.section.7.4.11.p.1">The server is refusing to process a request because the request representation is larger than the server is willing or able
    2013          to process. The server <em class="bcp14">MAY</em> close the connection to prevent the client from continuing the request.
    2014       </p>
    2015       <p id="rfc.section.7.4.11.p.2">If the condition is temporary, the server <em class="bcp14">SHOULD</em> include a Retry-After header field to indicate that it is temporary and after what time the client <em class="bcp14">MAY</em> try again.
    2016       </p>
    2017       <div id="rfc.iref.48"></div>
    2018       <div id="rfc.iref.s.28"></div>
    2019       <h3 id="rfc.section.7.4.12"><a href="#rfc.section.7.4.12">7.4.12</a>&nbsp;<a id="status.414" href="#status.414">414 URI Too Long</a></h3>
    2020       <p id="rfc.section.7.4.12.p.1">The server is refusing to service the request because the effective request URI is longer than the server is willing to interpret.
    2021          This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long
    2022          query information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that
    2023          points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present
    2024          in some servers using fixed-length buffers for reading or manipulating the request-target.
    2025       </p>
    2026       <div id="rfc.iref.49"></div>
    2027       <div id="rfc.iref.s.29"></div>
    2028       <h3 id="rfc.section.7.4.13"><a href="#rfc.section.7.4.13">7.4.13</a>&nbsp;<a id="status.415" href="#status.415">415 Unsupported Media Type</a></h3>
    2029       <p id="rfc.section.7.4.13.p.1">The server is refusing to service the request because the request payload is in a format not supported by this request method
    2030          on the target resource.
    2031       </p>
    2032       <div id="rfc.iref.50"></div>
    2033       <div id="rfc.iref.s.30"></div>
    2034       <h3 id="rfc.section.7.4.14"><a href="#rfc.section.7.4.14">7.4.14</a>&nbsp;<a id="status.417" href="#status.417">417 Expectation Failed</a></h3>
    2035       <p id="rfc.section.7.4.14.p.1">The expectation given in an Expect header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;10.3</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
    2036          not be met by the next-hop server.
    2037       </p>
    2038       <div id="rfc.iref.51"></div>
    2039       <div id="rfc.iref.s.31"></div>
    2040       <h3 id="rfc.section.7.4.15"><a href="#rfc.section.7.4.15">7.4.15</a>&nbsp;<a id="status.426" href="#status.426">426 Upgrade Required</a></h3>
    2041       <p id="rfc.section.7.4.15.p.1">The request can not be completed without a prior protocol upgrade. This response <em class="bcp14">MUST</em> include an Upgrade header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 6.5</a> of <a href="#Part1" id="rfc.xref.Part1.36"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) specifying the required protocols.
    2042       </p>
    2043       <div id="rfc.figure.u.8"></div>
    2044       <p>Example:</p>  <pre class="text">HTTP/1.1 426 Upgrade Required
     1725      <div id="status.codes">
     1726         <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a href="#status.codes">Status Code Definitions</a></h1>
     1727         <p id="rfc.section.7.p.1">The first digit of the status-code defines the class of response. The last two digits do not have any categorization role.
     1728            There are 5 values for the first digit:
     1729         </p>
     1730         <ul>
     1731            <li>1xx: Informational - Request received, continuing process</li>
     1732            <li>2xx: Success - The action was successfully received, understood, and accepted</li>
     1733            <li>3xx: Redirection - Further action must be taken in order to complete the request</li>
     1734            <li>4xx: Client Error - The request contains bad syntax or cannot be fulfilled</li>
     1735            <li>5xx: Server Error - The server failed to fulfill an apparently valid request</li>
     1736         </ul>
     1737         <p id="rfc.section.7.p.2">Each status-code is described below, including any metadata required in the response.</p>
     1738         <p id="rfc.section.7.p.3">For most status codes the response can carry a payload, in which case a Content-Type header field indicates the payload's
     1739            media type (<a href="p3-payload.html#header.content-type" title="Content-Type">Section 6.8</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
     1740         </p>
     1741         <div id="status.1xx">
     1742            <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a href="#status.1xx">Informational 1xx</a></h2>
     1743            <p id="rfc.section.7.1.p.1">This class of status code indicates a provisional response, consisting only of the status-line and optional header fields,
     1744               and is terminated by an empty line. There are no required header fields for this class of status code. Since HTTP/1.0 did
     1745               not define any 1xx status codes, servers <em class="bcp14">MUST NOT</em> send a 1xx response to an HTTP/1.0 client except under experimental conditions.
     1746            </p>
     1747            <p id="rfc.section.7.1.p.2">A client <em class="bcp14">MUST</em> be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100
     1748               (Continue) status message. Unexpected 1xx status responses <em class="bcp14">MAY</em> be ignored by a user agent.
     1749            </p>
     1750            <p id="rfc.section.7.1.p.3">Proxies <em class="bcp14">MUST</em> forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself
     1751               requested the generation of the 1xx response. (For example, if a proxy adds a "Expect: 100-continue" field when it forwards
     1752               a request, then it need not forward the corresponding 100 (Continue) response(s).)
     1753            </p>
     1754            <div id="status.100">
     1755               <div id="rfc.iref.1.1"></div>
     1756               <div id="rfc.iref.s.2"></div>
     1757               <h3 id="rfc.section.7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;<a href="#status.100">100 Continue</a></h3>
     1758               <p id="rfc.section.7.1.1.p.1">The client <em class="bcp14">SHOULD</em> continue with its request. This interim response is used to inform the client that the initial part of the request has been
     1759                  received and has not yet been rejected by the server. The client <em class="bcp14">SHOULD</em> continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The
     1760                  server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.32"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code.
     1761               </p>
     1762            </div>
     1763            <div id="status.101">
     1764               <div id="rfc.iref.1.2"></div>
     1765               <div id="rfc.iref.s.3"></div>
     1766               <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a href="#status.101">101 Switching Protocols</a></h3>
     1767               <p id="rfc.section.7.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 6.5</a> of <a href="#Part1" id="rfc.xref.Part1.33"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined
     1768                  by the response's Upgrade header field immediately after the empty line which terminates the 101 response.
     1769               </p>
     1770               <p id="rfc.section.7.1.2.p.2">The protocol <em class="bcp14">SHOULD</em> be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over
     1771                  older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use
     1772                  such features.
     1773               </p>
     1774            </div>
     1775         </div>
     1776         <div id="status.2xx">
     1777            <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a href="#status.2xx">Successful 2xx</a></h2>
     1778            <p id="rfc.section.7.2.p.1">This class of status code indicates that the client's request was successfully received, understood, and accepted.</p>
     1779            <div id="status.200">
     1780               <div id="rfc.iref.2.1"></div>
     1781               <div id="rfc.iref.s.4"></div>
     1782               <h3 id="rfc.section.7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;<a href="#status.200">200 OK</a></h3>
     1783               <p id="rfc.section.7.2.1.p.1">The request has succeeded. The payload returned with the response is dependent on the method used in the request, for example: </p>
     1784               <dl>
     1785                  <dt>GET</dt>
     1786                  <dd>a representation of the target resource is sent in the response;</dd>
     1787                  <dt>HEAD</dt>
     1788                  <dd>the same representation as GET, except without the message body;</dd>
     1789                  <dt>POST</dt>
     1790                  <dd>a representation describing or containing the result of the action;</dd>
     1791                  <dt>TRACE</dt>
     1792                  <dd>a representation containing the request message as received by the end server.</dd>
     1793               </dl>
     1794               <p id="rfc.section.7.2.1.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.11"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 200 responses.
     1795               </p>
     1796            </div>
     1797            <div id="status.201">
     1798               <div id="rfc.iref.2.2"></div>
     1799               <div id="rfc.iref.s.5"></div>
     1800               <h3 id="rfc.section.7.2.2"><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;<a href="#status.201">201 Created</a></h3>
     1801               <p id="rfc.section.7.2.2.p.1">The request has been fulfilled and has resulted in a new resource being created.</p>
     1802               <p id="rfc.section.7.2.2.p.2">The newly created resource is typically linked to from the response payload, with the most relevant URI also being carried
     1803                  in the Location header field. If the newly created resource's URI is the same as the Effective Request URI, this information
     1804                  can be omitted (e.g., in the case of a response to a PUT request).
     1805               </p>
     1806               <p id="rfc.section.7.2.2.p.3">The origin server <em class="bcp14">MUST</em> create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server <em class="bcp14">SHOULD</em> respond with 202 (Accepted) response instead.
     1807               </p>
     1808               <p id="rfc.section.7.2.2.p.4">A 201 response <em class="bcp14">MAY</em> contain an ETag response header field indicating the current value of the entity-tag for the representation of the resource
     1809                  just created (see <a href="p4-conditional.html#header.etag" title="ETag">Section 2.3</a> of <a href="#Part4" id="rfc.xref.Part4.9"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>).
     1810               </p>
     1811            </div>
     1812            <div id="status.202">
     1813               <div id="rfc.iref.2.3"></div>
     1814               <div id="rfc.iref.s.6"></div>
     1815               <h3 id="rfc.section.7.2.3"><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;<a href="#status.202">202 Accepted</a></h3>
     1816               <p id="rfc.section.7.2.3.p.1">The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually
     1817                  be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status
     1818                  code from an asynchronous operation such as this.
     1819               </p>
     1820               <p id="rfc.section.7.2.3.p.2">The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process
     1821                  (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the
     1822                  server persist until the process is completed. The representation returned with this response <em class="bcp14">SHOULD</em> include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the
     1823                  user can expect the request to be fulfilled.
     1824               </p>
     1825            </div>
     1826            <div id="status.203">
     1827               <div id="rfc.iref.2.4"></div>
     1828               <div id="rfc.iref.s.7"></div>
     1829               <h3 id="rfc.section.7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></h3>
     1830               <p id="rfc.section.7.2.4.p.1">The representation in the response has been transformed or otherwise modified by a transforming proxy (<a href="p1-messaging.html#intermediaries" title="Intermediaries">Section 2.3</a> of <a href="#Part1" id="rfc.xref.Part1.34"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). Note that the behavior of transforming intermediaries is controlled by the no-transform Cache-Control directive (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 3.2</a> of <a href="#Part6" id="rfc.xref.Part6.12"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
     1831               </p>
     1832               <p id="rfc.section.7.2.4.p.2">This status code is only appropriate when the response status code would have been 200 (OK) otherwise. When the status code
     1833                  before transformation would have been different, the 214 Transformation Applied warn-code (<a href="p6-cache.html#header.warning" title="Warning">Section 3.6</a> of <a href="#Part6" id="rfc.xref.Part6.13"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) is appropriate.
     1834               </p>
     1835               <p id="rfc.section.7.2.4.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.14"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 203 responses.
     1836               </p>
     1837            </div>
     1838            <div id="status.204">
     1839               <div id="rfc.iref.2.5"></div>
     1840               <div id="rfc.iref.s.8"></div>
     1841               <h3 id="rfc.section.7.2.5"><a href="#rfc.section.7.2.5">7.2.5</a>&nbsp;<a href="#status.204">204 No Content</a></h3>
     1842               <p id="rfc.section.7.2.5.p.1">The 204 (No Content) status code indicates that the server has successfully fulfilled the request and that there is no additional
     1843                  content to return in the response payload body. Metadata in the response header fields refer to the target resource and its
     1844                  current representation after the requested action.
     1845               </p>
     1846               <p id="rfc.section.7.2.5.p.2">For example, if a 204 status code is received in response to a PUT request and the response contains an ETag header field,
     1847                  then the PUT was successful and the ETag field-value contains the entity-tag for the new representation of that target resource.
     1848               </p>
     1849               <p id="rfc.section.7.2.5.p.3">The 204 response allows a server to indicate that the action has been successfully applied to the target resource while implying
     1850                  that the user agent <em class="bcp14">SHOULD NOT</em> traverse away from its current "document view" (if any). The server assumes that the user agent will provide some indication
     1851                  of the success to its user, in accord with its own interface, and apply any new or updated metadata in the response to the
     1852                  active representation.
     1853               </p>
     1854               <p id="rfc.section.7.2.5.p.4">For example, a 204 status code is commonly used with document editing interfaces corresponding to a "save" action, such that
     1855                  the document being saved remains available to the user for editing. It is also frequently used with interfaces that expect
     1856                  automated data transfers to be prevalent, such as within distributed version control systems.
     1857               </p>
     1858               <p id="rfc.section.7.2.5.p.5">The 204 response <em class="bcp14">MUST NOT</em> include a message body, and thus is always terminated by the first empty line after the header fields.
     1859               </p>
     1860            </div>
     1861            <div id="status.205">
     1862               <div id="rfc.iref.2.6"></div>
     1863               <div id="rfc.iref.s.9"></div>
     1864               <h3 id="rfc.section.7.2.6"><a href="#rfc.section.7.2.6">7.2.6</a>&nbsp;<a href="#status.205">205 Reset Content</a></h3>
     1865               <p id="rfc.section.7.2.6.p.1">The server has fulfilled the request and the user agent <em class="bcp14">SHOULD</em> reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions
     1866                  to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate
     1867                  another input action.
     1868               </p>
     1869               <p id="rfc.section.7.2.6.p.2">The message body included with the response <em class="bcp14">MUST</em> be empty. Note that receivers still need to parse the response according to the algorithm defined in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.35"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>.
     1870               </p>
     1871            </div>
     1872         </div>
     1873         <div id="status.3xx">
     1874            <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a>&nbsp;<a href="#status.3xx">Redirection 3xx</a></h2>
     1875            <p id="rfc.section.7.3.p.1">This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request.
     1876               If the required action involves a subsequent HTTP request, it <em class="bcp14">MAY</em> be carried out by the user agent without interaction with the user if and only if the method used in the second request is
     1877               known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>.
     1878            </p>
     1879            <p id="rfc.section.7.3.p.2">There are several types of redirects: </p>
     1880            <ol>
     1881               <li>
     1882                  <p>Redirects of the request to another URI, either temporarily or permanently. The new URI is specified in the Location header
     1883                     field. In this specification, the status codes 301 (Moved Permanently), 302 (Found), and 307 (Temporary Redirect) fall under
     1884                     this category.
     1885                  </p>
     1886               </li>
     1887               <li>
     1888                  <p>Redirection to a new location that represents an indirect response to the request, such as the result of a POST operation
     1889                     to be retrieved with a subsequent GET request. This is status code 303 (See Other).
     1890                  </p>
     1891               </li>
     1892               <li>
     1893                  <p>Redirection offering a choice of matching resources for use by agent-driven content negotiation (<a href="p3-payload.html#agent-driven.negotiation" title="Agent-driven Negotiation">Section 5.2</a> of <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). This is status code 300 (Multiple Choices).
     1894                  </p>
     1895               </li>
     1896               <li>
     1897                  <p>Other kinds of redirection, such as to a cached result (status code 304 (Not Modified), see <a href="p4-conditional.html#status.304" title="304 Not Modified">Section 4.1</a> of <a href="#Part4" id="rfc.xref.Part4.10"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>).
     1898                  </p>
     1899               </li>
     1900            </ol>
     1901            <div class="note" id="rfc.section.7.3.p.3">
     1902               <p><b>Note:</b> In HTTP/1.0, only the status codes 301 (Moved Permanently) and 302 (Found) were defined for the first type of redirect, and
     1903                  the second type did not exist at all (<a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a>, <a href="https://tools.ietf.org/html/rfc1945#section-9.3">Section 9.3</a>). However it turned out that web forms using POST expected redirects to change the operation for the subsequent request to
     1904                  retrieval (GET). To address this use case, HTTP/1.1 introduced the second type of redirect with the status code 303 (See Other)
     1905                  (<a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="https://tools.ietf.org/html/rfc2068#section-10.3.4">Section 10.3.4</a>). As user agents did not change their behavior to maintain backwards compatibility, the first revision of HTTP/1.1 added
     1906                  yet another status code, 307 (Temporary Redirect), for which the backwards compatibility problems did not apply (<a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="https://tools.ietf.org/html/rfc2616#section-10.3.8">Section 10.3.8</a>). Over 10 years later, most user agents still do method rewriting for status codes 301 and 302, therefore this specification
     1907                  makes that behavior conformant in case the original request was POST.
     1908               </p>
     1909            </div>
     1910            <p id="rfc.section.7.3.p.4">A Location header field on a 3xx response indicates that a client <em class="bcp14">MAY</em> automatically redirect to the URI provided; see <a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;10.5</a>.
     1911            </p>
     1912            <p id="rfc.section.7.3.p.5">Note that for methods not known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;6.1.1</a>, automatic redirection needs to done with care, since the redirect might change the conditions under which the request was
     1913               issued.
     1914            </p>
     1915            <p id="rfc.section.7.3.p.6">Clients <em class="bcp14">SHOULD</em> detect and intervene in cyclical redirections (i.e., "infinite" redirection loops).
     1916            </p>
     1917            <div class="note" id="rfc.section.7.3.p.7">
     1918               <p><b>Note:</b> An earlier version of this specification recommended a maximum of five redirections (<a href="#RFC2068" id="rfc.xref.RFC2068.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="https://tools.ietf.org/html/rfc2068#section-10.3">Section 10.3</a>). Content developers need to be aware that some clients might implement such a fixed limitation.
     1919               </p>
     1920            </div>
     1921            <div id="status.300">
     1922               <div id="rfc.iref.3.1"></div>
     1923               <div id="rfc.iref.s.10"></div>
     1924               <h3 id="rfc.section.7.3.1"><a href="#rfc.section.7.3.1">7.3.1</a>&nbsp;<a href="#status.300">300 Multiple Choices</a></h3>
     1925               <p id="rfc.section.7.3.1.p.1">The target resource has more than one representation, each with its own specific location, and agent-driven negotiation information
     1926                  (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) is being provided so that the user (or user agent) can select a preferred representation by redirecting its request to that
     1927                  location.
     1928               </p>
     1929               <p id="rfc.section.7.3.1.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of representation metadata and location(s) from which the user or user agent can
     1930                  choose the one most appropriate. Depending upon the format and the capabilities of the user agent, selection of the most appropriate
     1931                  choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
     1932               </p>
     1933               <p id="rfc.section.7.3.1.p.3">If the server has a preferred choice of representation, it <em class="bcp14">SHOULD</em> include the specific URI for that representation in the Location field; user agents <em class="bcp14">MAY</em> use the Location field value for automatic redirection.
     1934               </p>
     1935               <p id="rfc.section.7.3.1.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.15"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 300 responses.
     1936               </p>
     1937            </div>
     1938            <div id="status.301">
     1939               <div id="rfc.iref.3.2"></div>
     1940               <div id="rfc.iref.s.11"></div>
     1941               <h3 id="rfc.section.7.3.2"><a href="#rfc.section.7.3.2">7.3.2</a>&nbsp;<a href="#status.301">301 Moved Permanently</a></h3>
     1942               <p id="rfc.section.7.3.2.p.1">The target resource has been assigned a new permanent URI and any future references to this resource <em class="bcp14">SHOULD</em> use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the effective
     1943                  request URI to one or more of the new references returned by the server, where possible.
     1944               </p>
     1945               <p id="rfc.section.7.3.2.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.16"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 301 responses.
     1946               </p>
     1947               <p id="rfc.section.7.3.2.p.3">The new permanent URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
     1948                  the new URI(s).
     1949               </p>
     1950               <div class="note" id="rfc.section.7.3.2.p.4">
     1951                  <p><b>Note:</b> For historic reasons, user agents <em class="bcp14">MAY</em> change the request method from POST to GET for the subsequent request. If this behavior is undesired, status code 307 (Temporary
     1952                     Redirect) can be used instead.
     1953                  </p>
     1954               </div>
     1955            </div>
     1956            <div id="status.302">
     1957               <div id="rfc.iref.3.3"></div>
     1958               <div id="rfc.iref.s.12"></div>
     1959               <h3 id="rfc.section.7.3.3"><a href="#rfc.section.7.3.3">7.3.3</a>&nbsp;<a href="#status.302">302 Found</a></h3>
     1960               <p id="rfc.section.7.3.3.p.1">The target resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
     1961               </p>
     1962               <p id="rfc.section.7.3.3.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
     1963                  the new URI(s).
     1964               </p>
     1965               <div class="note" id="rfc.section.7.3.3.p.3">
     1966                  <p><b>Note:</b> For historic reasons, user agents <em class="bcp14">MAY</em> change the request method from POST to GET for the subsequent request. If this behavior is undesired, status code 307 (Temporary
     1967                     Redirect) can be used instead.
     1968                  </p>
     1969               </div>
     1970            </div>
     1971            <div id="status.303">
     1972               <div id="rfc.iref.3.4"></div>
     1973               <div id="rfc.iref.s.13"></div>
     1974               <h3 id="rfc.section.7.3.4"><a href="#rfc.section.7.3.4">7.3.4</a>&nbsp;<a href="#status.303">303 See Other</a></h3>
     1975               <p id="rfc.section.7.3.4.p.1">The 303 status code indicates that the server is redirecting the user agent to a different resource, as indicated by a URI
     1976                  in the Location header field, that is intended to provide an indirect response to the original request. In order to satisfy
     1977                  the original request, a user agent <em class="bcp14">SHOULD</em> perform a retrieval request using the Location URI (a GET or HEAD request if using HTTP), which may itself be redirected further,
     1978                  and present the eventual result as an answer to the original request. Note that the new URI in the Location header field is
     1979                  not considered equivalent to the effective request URI.
     1980               </p>
     1981               <p id="rfc.section.7.3.4.p.2">This status code is generally applicable to any HTTP method. It is primarily used to allow the output of a POST action to
     1982                  redirect the user agent to a selected resource, since doing so provides the information corresponding to the POST response
     1983                  in a form that can be separately identified, bookmarked, and cached independent of the original request.
     1984               </p>
     1985               <p id="rfc.section.7.3.4.p.3">A 303 response to a GET request indicates that the requested resource does not have a representation of its own that can be
     1986                  transferred by the server over HTTP. The Location URI indicates a resource that is descriptive of the target resource, such
     1987                  that the follow-on representation might be useful to recipients without implying that it adequately represents the target
     1988                  resource. Note that answers to the questions of what can be represented, what representations are adequate, and what might
     1989                  be a useful description are outside the scope of HTTP and thus entirely determined by the URI owner(s).
     1990               </p>
     1991               <p id="rfc.section.7.3.4.p.4">Except for responses to a HEAD request, the representation of a 303 response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the Location URI.
     1992               </p>
     1993            </div>
     1994            <div id="status.305">
     1995               <div id="rfc.iref.3.5"></div>
     1996               <div id="rfc.iref.s.14"></div>
     1997               <h3 id="rfc.section.7.3.5"><a href="#rfc.section.7.3.5">7.3.5</a>&nbsp;<a href="#status.305">305 Use Proxy</a></h3>
     1998               <p id="rfc.section.7.3.5.p.1">The 305 status code was defined in a previous version of this specification (see <a href="#changes.from.rfc.2616" title="Changes from RFC 2616">Appendix&nbsp;A</a>), and is now deprecated.
     1999               </p>
     2000            </div>
     2001            <div id="status.306">
     2002               <div id="rfc.iref.3.6"></div>
     2003               <div id="rfc.iref.s.15"></div>
     2004               <h3 id="rfc.section.7.3.6"><a href="#rfc.section.7.3.6">7.3.6</a>&nbsp;<a href="#status.306">306 (Unused)</a></h3>
     2005               <p id="rfc.section.7.3.6.p.1">The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.</p>
     2006            </div>
     2007            <div id="status.307">
     2008               <div id="rfc.iref.3.7"></div>
     2009               <div id="rfc.iref.s.16"></div>
     2010               <h3 id="rfc.section.7.3.7"><a href="#rfc.section.7.3.7">7.3.7</a>&nbsp;<a href="#status.307">307 Temporary Redirect</a></h3>
     2011               <p id="rfc.section.7.3.7.p.1">The target resource resides temporarily under a different URI. Since the redirection can change over time, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
     2012               </p>
     2013               <p id="rfc.section.7.3.7.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. A response payload can contain a short hypertext note with a hyperlink to
     2014                  the new URI(s).
     2015               </p>
     2016               <div class="note" id="rfc.section.7.3.7.p.3">
     2017                  <p><b>Note:</b> This status code is similar to 302 Found, except that it does not allow rewriting the request method from POST to GET. This
     2018                     specification defines no equivalent counterpart for 301 Moved Permanently.
     2019                  </p>
     2020               </div>
     2021            </div>
     2022         </div>
     2023         <div id="status.4xx">
     2024            <h2 id="rfc.section.7.4"><a href="#rfc.section.7.4">7.4</a>&nbsp;<a href="#status.4xx">Client Error 4xx</a></h2>
     2025            <p id="rfc.section.7.4.p.1">The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD
     2026               request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
     2027               These status codes are applicable to any request method. User agents <em class="bcp14">SHOULD</em> display any included representation to the user.
     2028            </p>
     2029            <div id="status.400">
     2030               <div id="rfc.iref.4.1"></div>
     2031               <div id="rfc.iref.s.17"></div>
     2032               <h3 id="rfc.section.7.4.1"><a href="#rfc.section.7.4.1">7.4.1</a>&nbsp;<a href="#status.400">400 Bad Request</a></h3>
     2033               <p id="rfc.section.7.4.1.p.1">The server cannot or will not process the request, due to a client error (e.g., malformed syntax).</p>
     2034            </div>
     2035            <div id="status.402">
     2036               <div id="rfc.iref.4.2"></div>
     2037               <div id="rfc.iref.s.18"></div>
     2038               <h3 id="rfc.section.7.4.2"><a href="#rfc.section.7.4.2">7.4.2</a>&nbsp;<a href="#status.402">402 Payment Required</a></h3>
     2039               <p id="rfc.section.7.4.2.p.1">This code is reserved for future use.</p>
     2040            </div>
     2041            <div id="status.403">
     2042               <div id="rfc.iref.4.3"></div>
     2043               <div id="rfc.iref.s.19"></div>
     2044               <h3 id="rfc.section.7.4.3"><a href="#rfc.section.7.4.3">7.4.3</a>&nbsp;<a href="#status.403">403 Forbidden</a></h3>
     2045               <p id="rfc.section.7.4.3.p.1">The server understood the request, but refuses to authorize it. Providing different user authentication credentials might
     2046                  be successful, but any credentials that were provided in the request are insufficient. The request <em class="bcp14">SHOULD NOT</em> be repeated with the same credentials.
     2047               </p>
     2048               <p id="rfc.section.7.4.3.p.2">If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it <em class="bcp14">SHOULD</em> describe the reason for the refusal in the representation. If the server does not wish to make this information available
     2049                  to the client, the status code 404 (Not Found) <em class="bcp14">MAY</em> be used instead.
     2050               </p>
     2051            </div>
     2052            <div id="status.404">
     2053               <div id="rfc.iref.4.4"></div>
     2054               <div id="rfc.iref.s.20"></div>
     2055               <h3 id="rfc.section.7.4.4"><a href="#rfc.section.7.4.4">7.4.4</a>&nbsp;<a href="#status.404">404 Not Found</a></h3>
     2056               <p id="rfc.section.7.4.4.p.1">The server has not found anything matching the effective request URI. No indication is given of whether the condition is temporary
     2057                  or permanent. The 410 (Gone) status code <em class="bcp14">SHOULD</em> be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable
     2058                  and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request
     2059                  has been refused, or when no other response is applicable.
     2060               </p>
     2061            </div>
     2062            <div id="status.405">
     2063               <div id="rfc.iref.4.5"></div>
     2064               <div id="rfc.iref.s.21"></div>
     2065               <h3 id="rfc.section.7.4.5"><a href="#rfc.section.7.4.5">7.4.5</a>&nbsp;<a href="#status.405">405 Method Not Allowed</a></h3>
     2066               <p id="rfc.section.7.4.5.p.1">The method specified in the request-line is not allowed for the target resource. The response <em class="bcp14">MUST</em> include an Allow header field containing a list of valid methods for the requested resource.
     2067               </p>
     2068            </div>
     2069            <div id="status.406">
     2070               <div id="rfc.iref.4.6"></div>
     2071               <div id="rfc.iref.s.22"></div>
     2072               <h3 id="rfc.section.7.4.6"><a href="#rfc.section.7.4.6">7.4.6</a>&nbsp;<a href="#status.406">406 Not Acceptable</a></h3>
     2073               <p id="rfc.section.7.4.6.p.1">The resource identified by the request is only capable of generating response representations which have content characteristics
     2074                  not acceptable according to the Accept and Accept-* header fields sent in the request (see <a href="p3-payload.html#header.field.definitions" title="Header Field Definitions">Section 6</a> of <a href="#Part3" id="rfc.xref.Part3.12"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
     2075               </p>
     2076               <p id="rfc.section.7.4.6.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of available representation characteristics and location(s) from which the user
     2077                  or user agent can choose the one most appropriate. Depending upon the format and the capabilities of the user agent, selection
     2078                  of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
     2079               </p>
     2080               <div class="note" id="rfc.section.7.4.6.p.3">
     2081                  <p><b>Note:</b> HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept header fields sent in the
     2082                     request. In some cases, this might even be preferable to sending a 406 response. User agents are encouraged to inspect the
     2083                     header fields of an incoming response to determine if it is acceptable.
     2084                  </p>
     2085               </div>
     2086               <p id="rfc.section.7.4.6.p.4">If the response could be unacceptable, a user agent <em class="bcp14">SHOULD</em> temporarily stop receipt of more data and query the user for a decision on further actions.
     2087               </p>
     2088            </div>
     2089            <div id="status.408">
     2090               <div id="rfc.iref.4.7"></div>
     2091               <div id="rfc.iref.s.23"></div>
     2092               <h3 id="rfc.section.7.4.7"><a href="#rfc.section.7.4.7">7.4.7</a>&nbsp;<a href="#status.408">408 Request Timeout</a></h3>
     2093               <p id="rfc.section.7.4.7.p.1">The client did not produce a request within the time that the server was prepared to wait. The client <em class="bcp14">MAY</em> repeat the request without modifications at any later time.
     2094               </p>
     2095            </div>
     2096            <div id="status.409">
     2097               <div id="rfc.iref.4.8"></div>
     2098               <div id="rfc.iref.s.24"></div>
     2099               <h3 id="rfc.section.7.4.8"><a href="#rfc.section.7.4.8">7.4.8</a>&nbsp;<a href="#status.409">409 Conflict</a></h3>
     2100               <p id="rfc.section.7.4.8.p.1">The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in
     2101                  situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response
     2102                  body <em class="bcp14">SHOULD</em> include enough information for the user to recognize the source of the conflict. Ideally, the response representation would
     2103                  include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.
     2104               </p>
     2105               <p id="rfc.section.7.4.8.p.2">Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the representation
     2106                  being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might
     2107                  use the 409 response to indicate that it can't complete the request. In this case, the response representation would likely
     2108                  contain a list of the differences between the two versions.
     2109               </p>
     2110            </div>
     2111            <div id="status.410">
     2112               <div id="rfc.iref.4.9"></div>
     2113               <div id="rfc.iref.s.25"></div>
     2114               <h3 id="rfc.section.7.4.9"><a href="#rfc.section.7.4.9">7.4.9</a>&nbsp;<a href="#status.410">410 Gone</a></h3>
     2115               <p id="rfc.section.7.4.9.p.1">The target resource is no longer available at the server and no forwarding address is known. This condition is expected to
     2116                  be considered permanent. Clients with link editing capabilities <em class="bcp14">SHOULD</em> delete references to the effective request URI after user approval. If the server does not know, or has no facility to determine,
     2117                  whether or not the condition is permanent, the status code 404 (Not Found) <em class="bcp14">SHOULD</em> be used instead.
     2118               </p>
     2119               <p id="rfc.section.7.4.9.p.2">The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource
     2120                  is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event
     2121                  is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's
     2122                  site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time
     2123                  — that is left to the discretion of the server owner.
     2124               </p>
     2125               <p id="rfc.section.7.4.9.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.17"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 410 responses.
     2126               </p>
     2127            </div>
     2128            <div id="status.411">
     2129               <div id="rfc.iref.4.10"></div>
     2130               <div id="rfc.iref.s.26"></div>
     2131               <h3 id="rfc.section.7.4.10"><a href="#rfc.section.7.4.10">7.4.10</a>&nbsp;<a href="#status.411">411 Length Required</a></h3>
     2132               <p id="rfc.section.7.4.10.p.1">The server refuses to accept the request without a defined Content-Length. The client <em class="bcp14">MAY</em> repeat the request if it adds a valid Content-Length header field containing the length of the message body in the request
     2133                  message.
     2134               </p>
     2135            </div>
     2136            <div id="status.413">
     2137               <div id="rfc.iref.4.11"></div>
     2138               <div id="rfc.iref.s.27"></div>
     2139               <h3 id="rfc.section.7.4.11"><a href="#rfc.section.7.4.11">7.4.11</a>&nbsp;<a href="#status.413">413 Request Representation Too Large</a></h3>
     2140               <p id="rfc.section.7.4.11.p.1">The server is refusing to process a request because the request representation is larger than the server is willing or able
     2141                  to process. The server <em class="bcp14">MAY</em> close the connection to prevent the client from continuing the request.
     2142               </p>
     2143               <p id="rfc.section.7.4.11.p.2">If the condition is temporary, the server <em class="bcp14">SHOULD</em> include a Retry-After header field to indicate that it is temporary and after what time the client <em class="bcp14">MAY</em> try again.
     2144               </p>
     2145            </div>
     2146            <div id="status.414">
     2147               <div id="rfc.iref.4.12"></div>
     2148               <div id="rfc.iref.s.28"></div>
     2149               <h3 id="rfc.section.7.4.12"><a href="#rfc.section.7.4.12">7.4.12</a>&nbsp;<a href="#status.414">414 URI Too Long</a></h3>
     2150               <p id="rfc.section.7.4.12.p.1">The server is refusing to service the request because the effective request URI is longer than the server is willing to interpret.
     2151                  This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long
     2152                  query information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that
     2153                  points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present
     2154                  in some servers using fixed-length buffers for reading or manipulating the request-target.
     2155               </p>
     2156            </div>
     2157            <div id="status.415">
     2158               <div id="rfc.iref.4.13"></div>
     2159               <div id="rfc.iref.s.29"></div>
     2160               <h3 id="rfc.section.7.4.13"><a href="#rfc.section.7.4.13">7.4.13</a>&nbsp;<a href="#status.415">415 Unsupported Media Type</a></h3>
     2161               <p id="rfc.section.7.4.13.p.1">The server is refusing to service the request because the request payload is in a format not supported by this request method
     2162                  on the target resource.
     2163               </p>
     2164            </div>
     2165            <div id="status.417">
     2166               <div id="rfc.iref.4.14"></div>
     2167               <div id="rfc.iref.s.30"></div>
     2168               <h3 id="rfc.section.7.4.14"><a href="#rfc.section.7.4.14">7.4.14</a>&nbsp;<a href="#status.417">417 Expectation Failed</a></h3>
     2169               <p id="rfc.section.7.4.14.p.1">The expectation given in an Expect header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;10.3</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
     2170                  not be met by the next-hop server.
     2171               </p>
     2172            </div>
     2173            <div id="status.426">
     2174               <div id="rfc.iref.4.15"></div>
     2175               <div id="rfc.iref.s.31"></div>
     2176               <h3 id="rfc.section.7.4.15"><a href="#rfc.section.7.4.15">7.4.15</a>&nbsp;<a href="#status.426">426 Upgrade Required</a></h3>
     2177               <p id="rfc.section.7.4.15.p.1">The request can not be completed without a prior protocol upgrade. This response <em class="bcp14">MUST</em> include an Upgrade header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 6.5</a> of <a href="#Part1" id="rfc.xref.Part1.36"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) specifying the required protocols.
     2178               </p>
     2179               <div id="rfc.figure.u.8"></div>
     2180               <p>Example:</p><pre class="text">HTTP/1.1 426 Upgrade Required
    20452181Upgrade: HTTP/3.0
    20462182Connection: Upgrade
     
    20502186<span id="s426body">This service requires use of the HTTP/3.0 protocol.
    20512187</span></pre><p id="rfc.section.7.4.15.p.3">The server <em class="bcp14">SHOULD</em> include a message body in the 426 response which indicates in human readable form the reason for the error and describes any
    2052          alternative courses which may be available to the user.
    2053       </p>
    2054       <h2 id="rfc.section.7.5"><a href="#rfc.section.7.5">7.5</a>&nbsp;<a id="status.5xx" href="#status.5xx">Server Error 5xx</a></h2>
    2055       <p id="rfc.section.7.5.p.1">Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable
    2056          of performing the request. Except when responding to a HEAD request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
    2057          User agents <em class="bcp14">SHOULD</em> display any included representation to the user. These response codes are applicable to any request method.
    2058       </p>
    2059       <div id="rfc.iref.52"></div>
    2060       <div id="rfc.iref.s.32"></div>
    2061       <h3 id="rfc.section.7.5.1"><a href="#rfc.section.7.5.1">7.5.1</a>&nbsp;<a id="status.500" href="#status.500">500 Internal Server Error</a></h3>
    2062       <p id="rfc.section.7.5.1.p.1">The server encountered an unexpected condition which prevented it from fulfilling the request.</p>
    2063       <div id="rfc.iref.53"></div>
    2064       <div id="rfc.iref.s.33"></div>
    2065       <h3 id="rfc.section.7.5.2"><a href="#rfc.section.7.5.2">7.5.2</a>&nbsp;<a id="status.501" href="#status.501">501 Not Implemented</a></h3>
    2066       <p id="rfc.section.7.5.2.p.1">The server does not support the functionality required to fulfill the request. This is the appropriate response when the server
    2067          does not recognize the request method and is not capable of supporting it for any resource.
    2068       </p>
    2069       <div id="rfc.iref.54"></div>
    2070       <div id="rfc.iref.s.34"></div>
    2071       <h3 id="rfc.section.7.5.3"><a href="#rfc.section.7.5.3">7.5.3</a>&nbsp;<a id="status.502" href="#status.502">502 Bad Gateway</a></h3>
    2072       <p id="rfc.section.7.5.3.p.1">The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting
    2073          to fulfill the request.
    2074       </p>
    2075       <div id="rfc.iref.55"></div>
    2076       <div id="rfc.iref.s.35"></div>
    2077       <h3 id="rfc.section.7.5.4"><a href="#rfc.section.7.5.4">7.5.4</a>&nbsp;<a id="status.503" href="#status.503">503 Service Unavailable</a></h3>
    2078       <p id="rfc.section.7.5.4.p.1">The server is currently unable to handle the request due to a temporary overloading or maintenance of the server.</p>
    2079       <p id="rfc.section.7.5.4.p.2">The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the
    2080          delay <em class="bcp14">MAY</em> be indicated in a Retry-After header field (<a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;10.8</a>). If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
    2081       </p>
    2082       <div class="note" id="rfc.section.7.5.4.p.3">
    2083          <p> <b>Note:</b> The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers might
    2084             wish to simply refuse the connection.
    2085          </p>
     2188                  alternative courses which may be available to the user.
     2189               </p>
     2190            </div>
     2191         </div>
     2192         <div id="status.5xx">
     2193            <h2 id="rfc.section.7.5"><a href="#rfc.section.7.5">7.5</a>&nbsp;<a href="#status.5xx">Server Error 5xx</a></h2>
     2194            <p id="rfc.section.7.5.p.1">Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable
     2195               of performing the request. Except when responding to a HEAD request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
     2196               User agents <em class="bcp14">SHOULD</em> display any included representation to the user. These response codes are applicable to any request method.
     2197            </p>
     2198            <div id="status.500">
     2199               <div id="rfc.iref.5.1"></div>
     2200               <div id="rfc.iref.s.32"></div>
     2201               <h3 id="rfc.section.7.5.1"><a href="#rfc.section.7.5.1">7.5.1</a>&nbsp;<a href="#status.500">500 Internal Server Error</a></h3>
     2202               <p id="rfc.section.7.5.1.p.1">The server encountered an unexpected condition which prevented it from fulfilling the request.</p>
     2203            </div>
     2204            <div id="status.501">
     2205               <div id="rfc.iref.5.2"></div>
     2206               <div id="rfc.iref.s.33"></div>
     2207               <h3 id="rfc.section.7.5.2"><a href="#rfc.section.7.5.2">7.5.2</a>&nbsp;<a href="#status.501">501 Not Implemented</a></h3>
     2208               <p id="rfc.section.7.5.2.p.1">The server does not support the functionality required to fulfill the request. This is the appropriate response when the server
     2209                  does not recognize the request method and is not capable of supporting it for any resource.
     2210               </p>
     2211            </div>
     2212            <div id="status.502">
     2213               <div id="rfc.iref.5.3"></div>
     2214               <div id="rfc.iref.s.34"></div>
     2215               <h3 id="rfc.section.7.5.3"><a href="#rfc.section.7.5.3">7.5.3</a>&nbsp;<a href="#status.502">502 Bad Gateway</a></h3>
     2216               <p id="rfc.section.7.5.3.p.1">The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting
     2217                  to fulfill the request.
     2218               </p>
     2219            </div>
     2220            <div id="status.503">
     2221               <div id="rfc.iref.5.4"></div>
     2222               <div id="rfc.iref.s.35"></div>
     2223               <h3 id="rfc.section.7.5.4"><a href="#rfc.section.7.5.4">7.5.4</a>&nbsp;<a href="#status.503">503 Service Unavailable</a></h3>
     2224               <p id="rfc.section.7.5.4.p.1">The server is currently unable to handle the request due to a temporary overloading or maintenance of the server.</p>
     2225               <p id="rfc.section.7.5.4.p.2">The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the
     2226                  delay <em class="bcp14">MAY</em> be indicated in a Retry-After header field (<a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;10.8</a>). If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
     2227               </p>
     2228               <div class="note" id="rfc.section.7.5.4.p.3">
     2229                  <p><b>Note:</b> The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers might
     2230                     wish to simply refuse the connection.
     2231                  </p>
     2232               </div>
     2233            </div>
     2234            <div id="status.504">
     2235               <div id="rfc.iref.5.5"></div>
     2236               <div id="rfc.iref.s.36"></div>
     2237               <h3 id="rfc.section.7.5.5"><a href="#rfc.section.7.5.5">7.5.5</a>&nbsp;<a href="#status.504">504 Gateway Timeout</a></h3>
     2238               <p id="rfc.section.7.5.5.p.1">The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the
     2239                  URI (e.g., HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed to access in attempting to complete the request.
     2240               </p>
     2241               <div class="note" id="rfc.section.7.5.5.p.2">
     2242                  <p><b>Note</b> to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.
     2243                  </p>
     2244               </div>
     2245            </div>
     2246            <div id="status.505">
     2247               <div id="rfc.iref.5.6"></div>
     2248               <div id="rfc.iref.s.37"></div>
     2249               <h3 id="rfc.section.7.5.6"><a href="#rfc.section.7.5.6">7.5.6</a>&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></h3>
     2250               <p id="rfc.section.7.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server
     2251                  is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described
     2252                  in <a href="p1-messaging.html#http.version" title="Protocol Versioning">Section 2.6</a> of <a href="#Part1" id="rfc.xref.Part1.37"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain a representation describing why that version is not supported and what other protocols are supported by that server.
     2253               </p>
     2254            </div>
     2255         </div>
    20862256      </div>
    2087       <div id="rfc.iref.56"></div>
    2088       <div id="rfc.iref.s.36"></div>
    2089       <h3 id="rfc.section.7.5.5"><a href="#rfc.section.7.5.5">7.5.5</a>&nbsp;<a id="status.504" href="#status.504">504 Gateway Timeout</a></h3>
    2090       <p id="rfc.section.7.5.5.p.1">The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the
    2091          URI (e.g., HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed to access in attempting to complete the request.
    2092       </p>
    2093       <div class="note" id="rfc.section.7.5.5.p.2">
    2094          <p> <b>Note</b> to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.
    2095          </p>
    2096       </div>
    2097       <div id="rfc.iref.57"></div>
    2098       <div id="rfc.iref.s.37"></div>
    2099       <h3 id="rfc.section.7.5.6"><a href="#rfc.section.7.5.6">7.5.6</a>&nbsp;<a id="status.505" href="#status.505">505 HTTP Version Not Supported</a></h3>
    2100       <p id="rfc.section.7.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server
    2101          is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described
    2102          in <a href="p1-messaging.html#http.version" title="Protocol Versioning">Section 2.6</a> of <a href="#Part1" id="rfc.xref.Part1.37"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain a representation describing why that version is not supported and what other protocols are supported by that server.
    2103       </p>
    2104       <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a id="http.date" href="#http.date">Date/Time Formats</a></h1>
    2105       <p id="rfc.section.8.p.1">HTTP applications have historically allowed three different formats for date/time stamps. However, the preferred format is
    2106          a fixed-length subset of that defined by <a href="#RFC1123" id="rfc.xref.RFC1123.1"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>:
    2107       </p>
    2108       <div id="rfc.figure.u.9"></div><pre class="text">Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
     2257      <div id="http.date">
     2258         <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a href="#http.date">Date/Time Formats</a></h1>
     2259         <p id="rfc.section.8.p.1">HTTP applications have historically allowed three different formats for date/time stamps. However, the preferred format is
     2260            a fixed-length subset of that defined by <a href="#RFC1123" id="rfc.xref.RFC1123.1"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>:
     2261         </p>
     2262         <div id="rfc.figure.u.9"></div><pre class="text">Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
    21092263</pre><p id="rfc.section.8.p.3">The other formats are described here only for compatibility with obsolete implementations.</p>
    2110       <div id="rfc.figure.u.10"></div><pre class="text">Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
     2264         <div id="rfc.figure.u.10"></div><pre class="text">Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
    21112265Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
    21122266</pre><p id="rfc.section.8.p.5">HTTP/1.1 clients and servers that parse a date value <em class="bcp14">MUST</em> accept all three formats (for compatibility with HTTP/1.0), though they <em class="bcp14">MUST</em> only generate the RFC 1123 format for representing HTTP-date values in header fields.
    2113       </p>
    2114       <p id="rfc.section.8.p.6">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated
    2115          Universal Time). This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for
    2116          time zone, and <em class="bcp14">MUST</em> be assumed when reading the asctime format. HTTP-date is case sensitive and <em class="bcp14">MUST NOT</em> include additional whitespace beyond that specifically included as SP in the grammar.
    2117       </p>
    2118       <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.6"></span>  <a href="#http.date" class="smpl">HTTP-date</a>    = <a href="#preferred.date.format" class="smpl">rfc1123-date</a> / <a href="#obsolete.date.formats" class="smpl">obs-date</a>
     2267         </p>
     2268         <p id="rfc.section.8.p.6">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated
     2269            Universal Time). This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for
     2270            time zone, and <em class="bcp14">MUST</em> be assumed when reading the asctime format. HTTP-date is case sensitive and <em class="bcp14">MUST NOT</em> include additional whitespace beyond that specifically included as SP in the grammar.
     2271         </p>
     2272         <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.6"></span>  <a href="#http.date" class="smpl">HTTP-date</a>    = <a href="#preferred.date.format" class="smpl">rfc1123-date</a> / <a href="#obsolete.date.formats" class="smpl">obs-date</a>
    21192273</pre><div id="preferred.date.format">
    2120          <p id="rfc.section.8.p.8">                    Preferred format:</p>
    2121       </div>
    2122       <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span><span id="rfc.iref.g.18"></span>  <a href="#preferred.date.format" class="smpl">rfc1123-date</a> = <a href="#preferred.date.format" class="smpl">day-name</a> "," <a href="#notation" class="smpl">SP</a> date1 <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">time-of-day</a> <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">GMT</a>
     2274            <p id="rfc.section.8.p.8">          Preferred format:</p>
     2275         </div>
     2276         <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span><span id="rfc.iref.g.18"></span>  <a href="#preferred.date.format" class="smpl">rfc1123-date</a> = <a href="#preferred.date.format" class="smpl">day-name</a> "," <a href="#notation" class="smpl">SP</a> date1 <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">time-of-day</a> <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">GMT</a>
    21232277  ; fixed length subset of the format defined in
    2124   ; <a href="http://tools.ietf.org/html/rfc1123#section-5.2.14">Section 5.2.14</a> of <a href="#RFC1123" id="rfc.xref.RFC1123.2"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>
     2278  ; <a href="https://tools.ietf.org/html/rfc1123#section-5.2.14">Section 5.2.14</a> of <a href="#RFC1123" id="rfc.xref.RFC1123.2"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>
    21252279 
    21262280  <a href="#preferred.date.format" class="smpl">day-name</a>     = %x4D.6F.6E ; "Mon", case-sensitive
     
    21582312  <a href="#preferred.date.format" class="smpl">minute</a>       = 2<a href="#notation" class="smpl">DIGIT</a>               
    21592313  <a href="#preferred.date.format" class="smpl">second</a>       = 2<a href="#notation" class="smpl">DIGIT</a>               
    2160 </pre><p id="rfc.section.8.p.10">The semantics of <a href="#preferred.date.format" class="smpl">day-name</a>, <a href="#preferred.date.format" class="smpl">day</a>, <a href="#preferred.date.format" class="smpl">month</a>, <a href="#preferred.date.format" class="smpl">year</a>, and <a href="#preferred.date.format" class="smpl">time-of-day</a> are the same as those defined for the RFC 5322 constructs with the corresponding name (<a href="#RFC5322" id="rfc.xref.RFC5322.1"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="http://tools.ietf.org/html/rfc5322#section-3.3">Section 3.3</a>).
    2161       </p>
    2162       <div id="obsolete.date.formats">
    2163          <p id="rfc.section.8.p.11">                Obsolete formats:</p>
    2164       </div>
    2165       <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.19"></span>  <a href="#obsolete.date.formats" class="smpl">obs-date</a>     = <a href="#obsolete.date.formats" class="smpl">rfc850-date</a> / <a href="#obsolete.date.formats" class="smpl">asctime-date</a>
     2314</pre><p id="rfc.section.8.p.10">The semantics of <a href="#preferred.date.format" class="smpl">day-name</a>, <a href="#preferred.date.format" class="smpl">day</a>, <a href="#preferred.date.format" class="smpl">month</a>, <a href="#preferred.date.format" class="smpl">year</a>, and <a href="#preferred.date.format" class="smpl">time-of-day</a> are the same as those defined for the RFC 5322 constructs with the corresponding name (<a href="#RFC5322" id="rfc.xref.RFC5322.1"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="https://tools.ietf.org/html/rfc5322#section-3.3">Section 3.3</a>).
     2315         </p>
     2316         <div id="obsolete.date.formats">
     2317            <p id="rfc.section.8.p.11">        Obsolete formats:</p>
     2318         </div>
     2319         <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.19"></span>  <a href="#obsolete.date.formats" class="smpl">obs-date</a>     = <a href="#obsolete.date.formats" class="smpl">rfc850-date</a> / <a href="#obsolete.date.formats" class="smpl">asctime-date</a>
    21662320</pre><div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.20"></span>  <a href="#obsolete.date.formats" class="smpl">rfc850-date</a>  = <a href="#obsolete.date.formats" class="smpl">day-name-l</a> "," <a href="#notation" class="smpl">SP</a> <a href="#obsolete.date.formats" class="smpl">date2</a> <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">time-of-day</a> <a href="#notation" class="smpl">SP</a> <a href="#preferred.date.format" class="smpl">GMT</a>
    21672321  <a href="#obsolete.date.formats" class="smpl">date2</a>        = <a href="#preferred.date.format" class="smpl">day</a> "-" <a href="#preferred.date.format" class="smpl">month</a> "-" 2<a href="#notation" class="smpl">DIGIT</a>
     
    21782332  <a href="#obsolete.date.formats" class="smpl">date3</a>        = <a href="#preferred.date.format" class="smpl">month</a> <a href="#notation" class="smpl">SP</a> ( 2<a href="#notation" class="smpl">DIGIT</a> / ( <a href="#notation" class="smpl">SP</a> 1<a href="#notation" class="smpl">DIGIT</a> ))
    21792333                 ; month day (e.g., Jun  2)
    2180 </pre><div class="note" id="rfc.section.8.p.15">
    2181          <p> <b>Note:</b> Recipients of date values are encouraged to be robust in accepting date values that might have been sent by non-HTTP applications,
    2182             as is sometimes the case when retrieving or posting messages via proxies/gateways to SMTP or NNTP.
    2183          </p>
     2334</pre><div class="note" id="rfc.section.8.p.15">
     2335            <p><b>Note:</b> Recipients of date values are encouraged to be robust in accepting date values that might have been sent by non-HTTP applications,
     2336               as is sometimes the case when retrieving or posting messages via proxies/gateways to SMTP or NNTP.
     2337            </p>
     2338         </div>
     2339         <div class="note" id="rfc.section.8.p.16">
     2340            <p><b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers
     2341               are not required to use these formats for user presentation, request logging, etc.
     2342            </p>
     2343         </div>
    21842344      </div>
    2185       <div class="note" id="rfc.section.8.p.16">
    2186          <p> <b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers
    2187             are not required to use these formats for user presentation, request logging, etc.
    2188          </p>
    2189       </div>
    2190       <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a id="product.tokens" href="#product.tokens">Product Tokens</a></h1>
    2191       <p id="rfc.section.9.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields
    2192          using product tokens also allow sub-products which form a significant part of the application to be listed, separated by whitespace.
    2193          By convention, the products are listed in order of their significance for identifying the application.
    2194       </p>
    2195       <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.22"></span><span id="rfc.iref.g.23"></span>  <a href="#product.tokens" class="smpl">product</a>         = <a href="#core.rules" class="smpl">token</a> ["/" <a href="#product.tokens" class="smpl">product-version</a>]
     2345      <div id="product.tokens">
     2346         <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a href="#product.tokens">Product Tokens</a></h1>
     2347         <p id="rfc.section.9.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields
     2348            using product tokens also allow sub-products which form a significant part of the application to be listed, separated by whitespace.
     2349            By convention, the products are listed in order of their significance for identifying the application.
     2350         </p>
     2351         <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.22"></span><span id="rfc.iref.g.23"></span>  <a href="#product.tokens" class="smpl">product</a>         = <a href="#core.rules" class="smpl">token</a> ["/" <a href="#product.tokens" class="smpl">product-version</a>]
    21962352  <a href="#product.tokens" class="smpl">product-version</a> = <a href="#core.rules" class="smpl">token</a>
    21972353</pre><p id="rfc.section.9.p.3">Examples:</p>
    2198       <div id="rfc.figure.u.17"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
     2354         <div id="rfc.figure.u.17"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
    21992355  Server: Apache/0.8.4
    22002356</pre><p id="rfc.section.9.p.5">Product tokens <em class="bcp14">SHOULD</em> be short and to the point. They <em class="bcp14">MUST NOT</em> be used for advertising or other non-essential information. Although any token octet <em class="bcp14">MAY</em> appear in a product-version, this token <em class="bcp14">SHOULD</em> only be used for a version identifier (i.e., successive versions of the same product <em class="bcp14">SHOULD</em> only differ in the product-version portion of the product value).
    2201       </p>
    2202       <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a id="header.field.definitions" href="#header.field.definitions">Header Field Definitions</a></h1>
    2203       <p id="rfc.section.10.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to request and response semantics.</p>
    2204       <div id="rfc.iref.a.1"></div>
    2205       <div id="rfc.iref.h.2"></div>
    2206       <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a id="header.allow" href="#header.allow">Allow</a></h2>
    2207       <p id="rfc.section.10.1.p.1">The "Allow" header field lists the set of methods advertised as supported by the target resource. The purpose of this field
    2208          is strictly to inform the recipient of valid request methods associated with the resource.
    2209       </p>
    2210       <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.24"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#method" class="smpl">method</a>
     2357         </p>
     2358      </div>
     2359      <div id="header.field.definitions">
     2360         <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a href="#header.field.definitions">Header Field Definitions</a></h1>
     2361         <p id="rfc.section.10.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to request and response semantics.</p>
     2362         <div id="header.allow">
     2363            <div id="rfc.iref.a.1"></div>
     2364            <div id="rfc.iref.h.2"></div>
     2365            <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a href="#header.allow">Allow</a></h2>
     2366            <p id="rfc.section.10.1.p.1">The "Allow" header field lists the set of methods advertised as supported by the target resource. The purpose of this field
     2367               is strictly to inform the recipient of valid request methods associated with the resource.
     2368            </p>
     2369            <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.24"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#method" class="smpl">method</a>
    22112370</pre><p id="rfc.section.10.1.p.3">Example of use:</p>
    2212       <div id="rfc.figure.u.19"></div><pre class="text">  Allow: GET, HEAD, PUT
     2371            <div id="rfc.figure.u.19"></div><pre class="text">  Allow: GET, HEAD, PUT
    22132372</pre><p id="rfc.section.10.1.p.5">The actual set of allowed methods is defined by the origin server at the time of each request.</p>
    2214       <p id="rfc.section.10.1.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field — it does not need to understand all the methods specified in order to handle them according
    2215          to the generic message handling rules.
    2216       </p>
    2217       <div id="rfc.iref.d.2"></div>
    2218       <div id="rfc.iref.h.3"></div>
    2219       <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a id="header.date" href="#header.date">Date</a></h2>
    2220       <p id="rfc.section.10.2.p.1">The "Date" header field represents the date and time at which the message was originated, having the same semantics as the
    2221          Origination Date Field (orig-date) defined in <a href="http://tools.ietf.org/html/rfc5322#section-3.6.1">Section 3.6.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a>. The field value is an HTTP-date, as defined in <a href="#http.date" title="Date/Time Formats">Section&nbsp;8</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.
    2222       </p>
    2223       <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.25"></span>  <a href="#header.date" class="smpl">Date</a> = <a href="#http.date" class="smpl">HTTP-date</a>
     2373            <p id="rfc.section.10.1.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field — it does not need to understand all the methods specified in order to handle them according
     2374               to the generic message handling rules.
     2375            </p>
     2376         </div>
     2377         <div id="header.date">
     2378            <div id="rfc.iref.d.2"></div>
     2379            <div id="rfc.iref.h.3"></div>
     2380            <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a href="#header.date">Date</a></h2>
     2381            <p id="rfc.section.10.2.p.1">The "Date" header field represents the date and time at which the message was originated, having the same semantics as the
     2382               Origination Date Field (orig-date) defined in <a href="https://tools.ietf.org/html/rfc5322#section-3.6.1">Section 3.6.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a>. The field value is an HTTP-date, as defined in <a href="#http.date" title="Date/Time Formats">Section&nbsp;8</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.
     2383            </p>
     2384            <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.25"></span>  <a href="#header.date" class="smpl">Date</a> = <a href="#http.date" class="smpl">HTTP-date</a>
    22242385</pre><p id="rfc.section.10.2.p.3">An example is</p>
    2225       <div id="rfc.figure.u.21"></div><pre class="text">  Date: Tue, 15 Nov 1994 08:12:31 GMT
     2386            <div id="rfc.figure.u.21"></div><pre class="text">  Date: Tue, 15 Nov 1994 08:12:31 GMT
    22262387</pre><p id="rfc.section.10.2.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases:
    2227       </p>
    2228       <ol>
    2229          <li>If the response status code is 100 (Continue) or 101 (Switching Protocols), the response <em class="bcp14">MAY</em> include a Date header field, at the server's option.
    2230          </li>
    2231          <li>If the response status code conveys a server error, e.g., 500 (Internal Server Error) or 503 (Service Unavailable), and it
    2232             is inconvenient or impossible to generate a valid Date.
    2233          </li>
    2234          <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field.
    2235          </li>
    2236       </ol>
    2237       <p id="rfc.section.10.2.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient.
    2238       </p>
    2239       <p id="rfc.section.10.2.p.7">Clients can use the Date header field as well; in order to keep request messages small, they are advised not to include it
    2240          when it doesn't convey any useful information (as is usually the case for requests that do not contain a payload).
    2241       </p>
    2242       <p id="rfc.section.10.2.p.8">The HTTP-date sent in a Date header field <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
    2243          of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the payload
    2244          is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic
    2245          value.
    2246       </p>
    2247       <div id="rfc.iref.e.1"></div>
    2248       <div id="rfc.iref.h.4"></div>
    2249       <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a id="header.expect" href="#header.expect">Expect</a></h2>
    2250       <p id="rfc.section.10.3.p.1">The "Expect" header field is used to indicate that particular server behaviors are required by the client.</p>
    2251       <div id="rfc.figure.u.22"></div><pre class="inline"><span id="rfc.iref.g.26"></span><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span><span id="rfc.iref.g.29"></span><span id="rfc.iref.g.30"></span>  <a href="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a>
     2388            </p>
     2389            <ol>
     2390               <li>If the response status code is 100 (Continue) or 101 (Switching Protocols), the response <em class="bcp14">MAY</em> include a Date header field, at the server's option.
     2391               </li>
     2392               <li>If the response status code conveys a server error, e.g., 500 (Internal Server Error) or 503 (Service Unavailable), and it
     2393                  is inconvenient or impossible to generate a valid Date.
     2394               </li>
     2395               <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field.
     2396               </li>
     2397            </ol>
     2398            <p id="rfc.section.10.2.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient.
     2399            </p>
     2400            <p id="rfc.section.10.2.p.7">Clients can use the Date header field as well; in order to keep request messages small, they are advised not to include it
     2401               when it doesn't convey any useful information (as is usually the case for requests that do not contain a payload).
     2402            </p>
     2403            <p id="rfc.section.10.2.p.8">The HTTP-date sent in a Date header field <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
     2404               of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the payload
     2405               is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic
     2406               value.
     2407            </p>
     2408         </div>
     2409         <div id="header.expect">
     2410            <div id="rfc.iref.e.1"></div>
     2411            <div id="rfc.iref.h.4"></div>
     2412            <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a href="#header.expect">Expect</a></h2>
     2413            <p id="rfc.section.10.3.p.1">The "Expect" header field is used to indicate that particular server behaviors are required by the client.</p>
     2414            <div id="rfc.figure.u.22"></div><pre class="inline"><span id="rfc.iref.g.26"></span><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span><span id="rfc.iref.g.29"></span><span id="rfc.iref.g.30"></span>  <a href="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a>
    22522415 
    22532416  <a href="#header.expect" class="smpl">expectation</a>  = <a href="#header.expect" class="smpl">expect-name</a> [ <a href="#core.rules" class="smpl">BWS</a> "=" <a href="#core.rules" class="smpl">BWS</a> <a href="#header.expect" class="smpl">expect-value</a> ]
     
    22582421  <a href="#header.expect" class="smpl">expect-value</a> = <a href="#core.rules" class="smpl">token</a> / <a href="#core.rules" class="smpl">quoted-string</a>
    22592422</pre><p id="rfc.section.10.3.p.3">If all received Expect header field(s) are syntactically valid but contain an expectation that the recipient does not understand
    2260          or cannot comply with, the recipient <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status code. A recipient of a syntactically invalid Expectation header field <em class="bcp14">MUST</em> respond with a 4xx status code other than 417.
    2261       </p>
    2262       <p id="rfc.section.10.3.p.4">The only expectation defined by this specification is:</p>
    2263       <p id="rfc.section.10.3.p.5"><span id="rfc.iref.89"></span><span id="rfc.iref.e.2"></span> 100-continue
    2264       </p>
    2265       <ul class="empty">
    2266          <li>The "100-continue" expectation is defined <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.38"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. It does not support any expect-params.
    2267          </li>
    2268       </ul>
    2269       <p id="rfc.section.10.3.p.6">Comparison is case-insensitive for names (expect-name), and case-sensitive for values (expect-value).</p>
    2270       <p id="rfc.section.10.3.p.7">The Expect mechanism is hop-by-hop: the above requirements apply to any server, including proxies. However, the Expect header
    2271          field itself is end-to-end; it <em class="bcp14">MUST</em> be forwarded if the request is forwarded.
    2272       </p>
    2273       <p id="rfc.section.10.3.p.8">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p>
    2274       <div id="rfc.iref.f.1"></div>
    2275       <div id="rfc.iref.h.5"></div>
    2276       <h2 id="rfc.section.10.4"><a href="#rfc.section.10.4">10.4</a>&nbsp;<a id="header.from" href="#header.from">From</a></h2>
    2277       <p id="rfc.section.10.4.p.1">The "From" header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>:
    2278       </p>
    2279       <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.31"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a>
     2423               or cannot comply with, the recipient <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status code. A recipient of a syntactically invalid Expectation header field <em class="bcp14">MUST</em> respond with a 4xx status code other than 417.
     2424            </p>
     2425            <p id="rfc.section.10.3.p.4">The only expectation defined by this specification is:</p>
     2426            <p id="rfc.section.10.3.p.5"><span id="rfc.iref.1.3"></span><span id="rfc.iref.e.2"></span> 100-continue
     2427            </p>
     2428            <ul class="empty">
     2429               <li>The "100-continue" expectation is defined <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.38"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. It does not support any expect-params.
     2430               </li>
     2431            </ul>
     2432            <p id="rfc.section.10.3.p.6">Comparison is case-insensitive for names (expect-name), and case-sensitive for values (expect-value).</p>
     2433            <p id="rfc.section.10.3.p.7">The Expect mechanism is hop-by-hop: the above requirements apply to any server, including proxies. However, the Expect header
     2434               field itself is end-to-end; it <em class="bcp14">MUST</em> be forwarded if the request is forwarded.
     2435            </p>
     2436            <p id="rfc.section.10.3.p.8">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p>
     2437         </div>
     2438         <div id="header.from">
     2439            <div id="rfc.iref.f.1"></div>
     2440            <div id="rfc.iref.h.5"></div>
     2441            <h2 id="rfc.section.10.4"><a href="#rfc.section.10.4">10.4</a>&nbsp;<a href="#header.from">From</a></h2>
     2442            <p id="rfc.section.10.4.p.1">The "From" header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="https://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>:
     2443            </p>
     2444            <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.31"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a>
    22802445 
    2281   <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in <a href="#RFC5322" id="rfc.xref.RFC5322.4"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a>&gt;
     2446  <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in <a href="#RFC5322" id="rfc.xref.RFC5322.4"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="https://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a>&gt;
    22822447</pre><p id="rfc.section.10.4.p.3">An example is:</p>
    2283       <div id="rfc.figure.u.24"></div><pre class="text">  From: webmaster@example.org
     2448            <div id="rfc.figure.u.24"></div><pre class="text">  From: webmaster@example.org
    22842449</pre><p id="rfc.section.10.4.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed
    2285          on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header field so that the person responsible for running the robot can be contacted if problems occur on the receiving
    2286          end.
    2287       </p>
    2288       <p id="rfc.section.10.4.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
    2289          issuer's address <em class="bcp14">SHOULD</em> be used.
    2290       </p>
    2291       <p id="rfc.section.10.4.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
    2292          security policy. It is strongly recommended that the user be able to disable, enable, and modify the value of this field at
    2293          any time prior to a request.
    2294       </p>
    2295       <div id="rfc.iref.l.1"></div>
    2296       <div id="rfc.iref.h.6"></div>
    2297       <h2 id="rfc.section.10.5"><a href="#rfc.section.10.5">10.5</a>&nbsp;<a id="header.location" href="#header.location">Location</a></h2>
    2298       <p id="rfc.section.10.5.p.1">The "Location" header field <em class="bcp14">MAY</em> be sent in responses to refer to a specific resource in accordance with the semantics of the status code.
    2299       </p>
    2300       <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.32"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a>
     2450               on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header field so that the person responsible for running the robot can be contacted if problems occur on the receiving
     2451               end.
     2452            </p>
     2453            <p id="rfc.section.10.4.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
     2454               issuer's address <em class="bcp14">SHOULD</em> be used.
     2455            </p>
     2456            <p id="rfc.section.10.4.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
     2457               security policy. It is strongly recommended that the user be able to disable, enable, and modify the value of this field at
     2458               any time prior to a request.
     2459            </p>
     2460         </div>
     2461         <div id="header.location">
     2462            <div id="rfc.iref.l.1"></div>
     2463            <div id="rfc.iref.h.6"></div>
     2464            <h2 id="rfc.section.10.5"><a href="#rfc.section.10.5">10.5</a>&nbsp;<a href="#header.location">Location</a></h2>
     2465            <p id="rfc.section.10.5.p.1">The "Location" header field <em class="bcp14">MAY</em> be sent in responses to refer to a specific resource in accordance with the semantics of the status code.
     2466            </p>
     2467            <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.32"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a>
    23012468</pre><p id="rfc.section.10.5.p.3">For 201 (Created) responses, the Location is the URI of the new resource which was created by the request. For 3xx responses,
    2302          the location <em class="bcp14">SHOULD</em> indicate the server's preferred URI for automatic redirection to the resource.
    2303       </p>
    2304       <p id="rfc.section.10.5.p.4">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, did contain a fragment identifier, and the final value does not,
    2305          then the original URI's fragment identifier is added to the final value.
    2306       </p>
    2307       <div id="rfc.figure.u.26"></div>
    2308       <p>For example, the original URI "http://www.example.org/~tim", combined with a field value given as:</p>  <pre class="text">  Location: /pub/WWW/People.html#tim
    2309 </pre>  <p>would result in a final value of "http://www.example.org/pub/WWW/People.html#tim"</p>
    2310       <div id="rfc.figure.u.27"></div>
    2311       <p>An original URI "http://www.example.org/index.html#larry", combined with a field value given as:</p>  <pre class="text">  Location: http://www.example.net/index.html
    2312 </pre>  <p>would result in a final value of "http://www.example.net/index.html#larry", preserving the original fragment identifier.</p>
    2313       <div class="note" id="rfc.section.10.5.p.7">
    2314          <p> <b>Note:</b> Some recipients attempt to recover from Location fields that are not valid URI references. This specification does not mandate
    2315             or define such processing, but does allow it (see <a href="#intro.conformance.and.error.handling" title="Conformance and Error Handling">Section&nbsp;1.1</a>).
    2316          </p>
    2317       </div>
    2318       <p id="rfc.section.10.5.p.8">There are circumstances in which a fragment identifier in a Location URI would not be appropriate. For instance, when it appears
    2319          in a 201 Created response, where the Location header field specifies the URI for the entire created resource.
    2320       </p>
    2321       <div class="note" id="rfc.section.10.5.p.9">
    2322          <p> <b>Note:</b> The Content-Location header field (<a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.13"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) differs from Location in that the Content-Location identifies the most specific resource corresponding to the enclosed representation.
    2323             It is therefore possible for a response to contain header fields for both Location and Content-Location.
    2324          </p>
    2325       </div>
    2326       <div id="rfc.iref.m.9"></div>
    2327       <div id="rfc.iref.h.7"></div>
    2328       <h2 id="rfc.section.10.6"><a href="#rfc.section.10.6">10.6</a>&nbsp;<a id="header.max-forwards" href="#header.max-forwards">Max-Forwards</a></h2>
    2329       <p id="rfc.section.10.6.p.1">The "Max-Forwards" header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.2" title="TRACE">Section&nbsp;6.8</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.2" title="OPTIONS">Section&nbsp;6.2</a>) methods to limit the number of times that the request is forwarded by proxies. This can be useful when the client is attempting
    2330          to trace a request which appears to be failing or looping mid-chain.
    2331       </p>
    2332       <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.33"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a>
     2469               the location <em class="bcp14">SHOULD</em> indicate the server's preferred URI for automatic redirection to the resource.
     2470            </p>
     2471            <p id="rfc.section.10.5.p.4">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, did contain a fragment identifier, and the final value does not,
     2472               then the original URI's fragment identifier is added to the final value.
     2473            </p>
     2474            <div id="rfc.figure.u.26"></div>
     2475            <p>For example, the original URI "http://www.example.org/~tim", combined with a field value given as:</p><pre class="text">  Location: /pub/WWW/People.html#tim
     2476</pre><p>would result in a final value of "http://www.example.org/pub/WWW/People.html#tim"</p>
     2477            <div id="rfc.figure.u.27"></div>
     2478            <p>An original URI "http://www.example.org/index.html#larry", combined with a field value given as:</p><pre class="text">  Location: http://www.example.net/index.html
     2479</pre><p>would result in a final value of "http://www.example.net/index.html#larry", preserving the original fragment identifier.</p>
     2480            <div class="note" id="rfc.section.10.5.p.7">
     2481               <p><b>Note:</b> Some recipients attempt to recover from Location fields that are not valid URI references. This specification does not mandate
     2482                  or define such processing, but does allow it (see <a href="#intro.conformance.and.error.handling" title="Conformance and Error Handling">Section&nbsp;1.1</a>).
     2483               </p>
     2484            </div>
     2485            <p id="rfc.section.10.5.p.8">There are circumstances in which a fragment identifier in a Location URI would not be appropriate. For instance, when it appears
     2486               in a 201 Created response, where the Location header field specifies the URI for the entire created resource.
     2487            </p>
     2488            <div class="note" id="rfc.section.10.5.p.9">
     2489               <p><b>Note:</b> The Content-Location header field (<a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.13"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) differs from Location in that the Content-Location identifies the most specific resource corresponding to the enclosed representation.
     2490                  It is therefore possible for a response to contain header fields for both Location and Content-Location.
     2491               </p>
     2492            </div>
     2493         </div>
     2494         <div id="header.max-forwards">
     2495            <div id="rfc.iref.m.9"></div>
     2496            <div id="rfc.iref.h.7"></div>
     2497            <h2 id="rfc.section.10.6"><a href="#rfc.section.10.6">10.6</a>&nbsp;<a href="#header.max-forwards">Max-Forwards</a></h2>
     2498            <p id="rfc.section.10.6.p.1">The "Max-Forwards" header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.2" title="TRACE">Section&nbsp;6.8</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.2" title="OPTIONS">Section&nbsp;6.2</a>) methods to limit the number of times that the request is forwarded by proxies. This can be useful when the client is attempting
     2499               to trace a request which appears to be failing or looping mid-chain.
     2500            </p>
     2501            <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.33"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a>
    23332502</pre><p id="rfc.section.10.6.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message can be forwarded.</p>
    2334       <p id="rfc.section.10.6.p.4">Each recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
    2335       </p>
    2336       <p id="rfc.section.10.6.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other request methods.
    2337       </p>
    2338       <div id="rfc.iref.r.1"></div>
    2339       <div id="rfc.iref.h.8"></div>
    2340       <h2 id="rfc.section.10.7"><a href="#rfc.section.10.7">10.7</a>&nbsp;<a id="header.referer" href="#header.referer">Referer</a></h2>
    2341       <p id="rfc.section.10.7.p.1">The "Referer" [sic] header field allows the client to specify the URI of the resource from which the target URI was obtained
    2342          (the "referrer", although the header field is misspelled.).
    2343       </p>
    2344       <p id="rfc.section.10.7.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
    2345          etc. It also allows obsolete or mistyped links to be traced for maintenance. Some servers use Referer as a means of controlling
    2346          where they allow links from (so-called "deep linking"), but legitimate requests do not always contain a Referer header field.
    2347       </p>
    2348       <p id="rfc.section.10.7.p.3">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard), the Referer
    2349          field <em class="bcp14">MUST</em> either be sent with the value "about:blank", or not be sent at all. Note that this requirement does not apply to sources with
    2350          non-HTTP URIs (e.g., FTP).
    2351       </p>
    2352       <div id="rfc.figure.u.29"></div><pre class="inline"><span id="rfc.iref.g.34"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
     2503            <p id="rfc.section.10.6.p.4">Each recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
     2504            </p>
     2505            <p id="rfc.section.10.6.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other request methods.
     2506            </p>
     2507         </div>
     2508         <div id="header.referer">
     2509            <div id="rfc.iref.r.1"></div>
     2510            <div id="rfc.iref.h.8"></div>
     2511            <h2 id="rfc.section.10.7"><a href="#rfc.section.10.7">10.7</a>&nbsp;<a href="#header.referer">Referer</a></h2>
     2512            <p id="rfc.section.10.7.p.1">The "Referer" [sic] header field allows the client to specify the URI of the resource from which the target URI was obtained
     2513               (the "referrer", although the header field is misspelled.).
     2514            </p>
     2515            <p id="rfc.section.10.7.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
     2516               etc. It also allows obsolete or mistyped links to be traced for maintenance. Some servers use Referer as a means of controlling
     2517               where they allow links from (so-called "deep linking"), but legitimate requests do not always contain a Referer header field.
     2518            </p>
     2519            <p id="rfc.section.10.7.p.3">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard), the Referer
     2520               field <em class="bcp14">MUST</em> either be sent with the value "about:blank", or not be sent at all. Note that this requirement does not apply to sources with
     2521               non-HTTP URIs (e.g., FTP).
     2522            </p>
     2523            <div id="rfc.figure.u.29"></div><pre class="inline"><span id="rfc.iref.g.34"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
    23532524</pre><p id="rfc.section.10.7.p.5">Example:</p>
    2354       <div id="rfc.figure.u.30"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
     2525            <div id="rfc.figure.u.30"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
    23552526</pre><p id="rfc.section.10.7.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;12.2</a> for security considerations.
    2356       </p>
    2357       <div id="rfc.iref.r.2"></div>
    2358       <div id="rfc.iref.h.9"></div>
    2359       <h2 id="rfc.section.10.8"><a href="#rfc.section.10.8">10.8</a>&nbsp;<a id="header.retry-after" href="#header.retry-after">Retry-After</a></h2>
    2360       <p id="rfc.section.10.8.p.1">The header "Retry-After" field can be used with a 503 (Service Unavailable) response to indicate how long the service is expected
    2361          to be unavailable to the requesting client. This field <em class="bcp14">MAY</em> also be used with any 3xx (Redirection) response to indicate the minimum time the user-agent is asked to wait before issuing
    2362          the redirected request.
    2363       </p>
    2364       <p id="rfc.section.10.8.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p>
    2365       <div id="rfc.figure.u.31"></div><pre class="inline"><span id="rfc.iref.g.35"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#http.date" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>
     2527            </p>
     2528         </div>
     2529         <div id="header.retry-after">
     2530            <div id="rfc.iref.r.2"></div>
     2531            <div id="rfc.iref.h.9"></div>
     2532            <h2 id="rfc.section.10.8"><a href="#rfc.section.10.8">10.8</a>&nbsp;<a href="#header.retry-after">Retry-After</a></h2>
     2533            <p id="rfc.section.10.8.p.1">The header "Retry-After" field can be used with a 503 (Service Unavailable) response to indicate how long the service is expected
     2534               to be unavailable to the requesting client. This field <em class="bcp14">MAY</em> also be used with any 3xx (Redirection) response to indicate the minimum time the user-agent is asked to wait before issuing
     2535               the redirected request.
     2536            </p>
     2537            <p id="rfc.section.10.8.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p>
     2538            <div id="rfc.figure.u.31"></div><pre class="inline"><span id="rfc.iref.g.35"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#http.date" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>
    23662539</pre><div id="rule.delta-seconds">
    2367          <p id="rfc.section.10.8.p.4"> Time spans are non-negative decimal integers, representing time in seconds.</p>
    2368       </div>
    2369       <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.36"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a>
     2540               <p id="rfc.section.10.8.p.4"> Time spans are non-negative decimal integers, representing time in seconds.</p>
     2541            </div>
     2542            <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.36"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a>
    23702543</pre><p id="rfc.section.10.8.p.6">Two examples of its use are</p>
    2371       <div id="rfc.figure.u.33"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
     2544            <div id="rfc.figure.u.33"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
    23722545  Retry-After: 120
    23732546</pre><p id="rfc.section.10.8.p.8">In the latter example, the delay is 2 minutes.</p>
    2374       <div id="rfc.iref.s.38"></div>
    2375       <div id="rfc.iref.h.10"></div>
    2376       <h2 id="rfc.section.10.9"><a href="#rfc.section.10.9">10.9</a>&nbsp;<a id="header.server" href="#header.server">Server</a></h2>
    2377       <p id="rfc.section.10.9.p.1">The "Server" header field contains information about the software used by the origin server to handle the request.</p>
    2378       <p id="rfc.section.10.9.p.2">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;9</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.39"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for
    2379          identifying the application.
    2380       </p>
    2381       <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.37"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
     2547         </div>
     2548         <div id="header.server">
     2549            <div id="rfc.iref.s.38"></div>
     2550            <div id="rfc.iref.h.10"></div>
     2551            <h2 id="rfc.section.10.9"><a href="#rfc.section.10.9">10.9</a>&nbsp;<a href="#header.server">Server</a></h2>
     2552            <p id="rfc.section.10.9.p.1">The "Server" header field contains information about the software used by the origin server to handle the request.</p>
     2553            <p id="rfc.section.10.9.p.2">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;9</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.39"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for
     2554               identifying the application.
     2555            </p>
     2556            <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.37"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
    23822557</pre><p id="rfc.section.10.9.p.4">Example:</p>
    2383       <div id="rfc.figure.u.35"></div><pre class="text">  Server: CERN/3.0 libwww/2.17
     2558            <div id="rfc.figure.u.35"></div><pre class="text">  Server: CERN/3.0 libwww/2.17
    23842559</pre><p id="rfc.section.10.9.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.40"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    2385       </p>
    2386       <div class="note" id="rfc.section.10.9.p.7">
    2387          <p> <b>Note:</b> Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
    2388             against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable
    2389             option.
    2390          </p>
     2560            </p>
     2561            <div class="note" id="rfc.section.10.9.p.7">
     2562               <p><b>Note:</b> Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
     2563                  against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable
     2564                  option.
     2565               </p>
     2566            </div>
     2567         </div>
     2568         <div id="header.user-agent">
     2569            <div id="rfc.iref.u.1"></div>
     2570            <div id="rfc.iref.h.11"></div>
     2571            <h2 id="rfc.section.10.10"><a href="#rfc.section.10.10">10.10</a>&nbsp;<a href="#header.user-agent">User-Agent</a></h2>
     2572            <p id="rfc.section.10.10.p.1">The "User-Agent" header field contains information about the user agent originating the request. User agents <em class="bcp14">SHOULD</em> include this field with requests.
     2573            </p>
     2574            <p id="rfc.section.10.10.p.2">Typically, it is used for statistical purposes, the tracing of protocol violations, and tailoring responses to avoid particular
     2575               user agent limitations.
     2576            </p>
     2577            <p id="rfc.section.10.10.p.3">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;9</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.41"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and its significant subproducts. By convention, the product tokens are listed in order of their significance
     2578               for identifying the application.
     2579            </p>
     2580            <p id="rfc.section.10.10.p.4">Because this field is usually sent on every request a user agent makes, implementations are encouraged not to include needlessly
     2581               fine-grained detail, and to limit (or even prohibit) the addition of subproducts by third parties. Overly long and detailed
     2582               User-Agent field values make requests larger and can also be used to identify ("fingerprint") the user against their wishes.
     2583            </p>
     2584            <p id="rfc.section.10.10.p.5">Likewise, implementations are encouraged not to use the product t