from: http://www.w3.org/Protocols/HTTP/1.1/draft-ietf-http-v11-spec-07.txt


INTERNET-DRAFT            HTTP/1.1             Monday, August 12, 1996


The individual values of the numeric status codes defined for HTTP/1.1,
and an example set of corresponding Reason-Phrase's, are presented
below. The reason phrases listed here are only recommended -- they may
be replaced by local equivalents without affecting the protocol.

       Status-Code    = "100"   ; Continue
                      | "101"   ; Switching Protocols
                      | "200"   ; OK
                      | "201"   ; Created
                      | "202"   ; Accepted
                      | "203"   ; Non-Authoritative Information
                      | "204"   ; No Content
                      | "205"   ; Reset Content
                      | "206"   ; Partial Content
                      | "300"   ; Multiple Choices
                      | "301"   ; Moved Permanently
                      | "302"   ; Moved Temporarily
                      | "303"   ; See Other
                      | "304"   ; Not Modified
                      | "305"   ; Use Proxy
                      | "400"   ; Bad Request
                      | "401"   ; Unauthorized
                      | "402"   ; Payment Required
                      | "403"   ; Forbidden
                      | "404"   ; Not Found
                      | "405"   ; Method Not Allowed
                      | "406"   ; Not Acceptable
                      | "407"   ; Proxy Authentication Required
                      | "408"   ; Request Time-out
                      | "409"   ; Conflict
                      | "410"   ; Gone
                      | "411"   ; Length Required
                      | "412"   ; Precondition Failed
                      | "413"   ; Request Entity Too Large
                      | "414"   ; Request-URI Too Large
                      | "415"   ; Unsupported Media Type
                      | "500"   ; Internal Server Error
                      | "501"   ; Not Implemented
                      | "502"   ; Bad Gateway
                      | "503"   ; Service Unavailable
                      | "504"   ; Gateway Time-out
                      | "505"   ; HTTP Version not supported
                      | extension-code

       extension-code = 3DIGIT

       Reason-Phrase  = *<TEXT, excluding CR, LF>

HTTP status codes are extensible. HTTP applications are not required to
understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST

Fielding, et al                                              [Page 38]