HTTP1.1 Notes 7, Status Code Definitions

Informational 1xx
This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line
-- 100 Continue
The client SHOULD continue with its request
-- 101 Switching Protocols
The server understands and is willing to comply with the client's request, via the Upgrade message header field, for a change in the application protocol being used on this connection

Successful 2xx
This class of status code indicates that the client's request was successfully received, understood, and accepted
-- 200 OK
The request has succeeded
-- 201 Created
The request has been fulfilled and resulted in a new resource being created
-- 202 Accepted
The request has been accepted for processing, but the processing has not been completed
-- 203 Non-Authoritative Information
The returned meta information in the entity-header is not the definitive set as available from the origin server, but is gathered from a local or a third-party copy
-- 204 No Content
The server has fulfilled the request but does not need to return an entity-body, and might want to return updated meta information
-- 205 Reset Content
The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent
-- 206 Partial Content
The server has fulfilled the partial GET request for the resource

Redirection 3xx
This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request
-- 300 Multiple Choices
The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location
-- 301 Moved Permanenty
The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs
-- 302 Found
The requested resource resides temporarily under a different URI
The temporary URI SHOULD be given by the Location field in the response
-- 303 See Other
The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource
-- 304 Not Modified
If the client has performed a conditional GET request and access is allowed, but the document has not been modified, the server SHOULD respond with this status code
-- 305 Use Proxy
The requested resource MUST be accessed through the proxy given by the Location field
-- 306 (Unused)
The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved
-- 307 Temporary Redirect
The requested resource resides temporarily under a different URI
The temporary URI SHOULD be given by the Location field in the response

Client Error 4xx
The 4xx class of status code is intended for cases in which the client seems to have erred
-- 400 Bad Request
The request could not be understood by the server due to malformed syntax
-- 401 Unauthorized
The request requires user authentication
-- 402 Payment Required
This code is reserved for future use
-- 403 Forbidden
The server understood the request, but is refusing to fulfill it
-- 404 Not Found
The server has not found anything matching the Request-URI
-- 405 Method Not Allowed
The method specified in the Request-Line is not allowed for the resource identified by the Request-URI
-- 406 Not Acceptable
The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request
-- 407 Proxy Authentication Required
This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy
-- 408 Request Timeout
The client did not produce a request within the time that the server was prepared to wait
-- 409 Conflict
The request could not be completed due to a conflict with the current state of the resource
-- 410 Gone
The requested resource is no longer available at the server and no forwarding address is known
-- 411 Length Required
The server refuses to accept the request without a defined Content- Length
-- 412 Precondition Failed
The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server
-- 413 Request Entity Too Large
The server is refusing to process a request because the request entity is larger than the server is willing or able to process
-- 414 Request-URI Too Long
The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret
-- 415 Unsupported Media Type
The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method
-- 416 Requested Range Not Satisfiable
A server SHOULD return a response with this status code if a request included a Range request-header field, and none of the range-specifier values in this field overlap the current extent of the selected resource, and the request did not include an If-Range request-header field
-- 417 Expectation Failed
The expectation given in an Expect request-header field could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could not be met by the next-hop server

Server Error 5xx
Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable of performing the request
-- 500 Internal Server Error
The server encountered an unexpected condition which prevented it from fulfilling the request
-- 501 Not Implemented
The server does not support the functionality required to fulfill the request
-- 502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request
-- 503 Service Unavailable
The server is currently unable to handle the request due to a temporary overloading or maintenance of the server
-- 504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request
-- 505 HTTP Version Not Supported
The server does not support, or refuses to support, the HTTP protocol version that was used in the request message