Error numbers and status codes

It is unlikely that you will see all of these errors or messages popping up in your browser window, as the browser usually handles them itself; you will probably only ever see those in the 400 and 500 range, such as 404 not found, 403 forbidden and 500 internal server error.

Informational 1xx
This class of status code indicates a provisional response.

100 Continue
The client may continue with its request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server.
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 protocol being used on this connection.

Successful 2xx
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 infomation is not the definitive version as available from the origin server, but is gathered from a local or a third-party copy. The set presented may be a subset or superset of the original version.
204 No Content
The server has fulfilled the request but there is no new information to send back.
205 Reset Content
The server has fulfilled the request and the user agent should reset the document view which caused the request to be generated. This response is primarily intended to allow input for actions 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 another input action.
206 Partial Content
The server has fulfilled the partial request for the resource.

Redirection 3xx
This class indicates that further action needs to be taken by the user agent in order to fulfill the request.

300 Multiple Choices
This response code is not directly used by HTTP/1.0 applications, but serves as the default for interpreting the 3xx class of responses.
301 Moved Permanently
The requested resource has been assigned a new permanent URL and any future references to this resource should be done using that URL.
302 Moved Temporarily
The requested resource resides temporarily under a different URL. Since the redirection may be altered on occasion, the client should continue to use this for future requests.
303 See Other
The response to the request can be found under a different URI
304 Not Modified
If the client has performed a conditional request and access is allowed, but the document has not been modified since the date and time specified in the If-Modified-Since field.
305 Use Proxy
The requested resource must be accessed through the proxy given by the Location field in the response. In other words, this is a proxy redirect.

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. The client should not repeat the request without modifications.
401 Unauthorized
The request requires user authentication. The response must include an authentification header field containing a challenge applicable to the requested resource.
402 Payment Required
This code is reserved for future use.
403 Forbidden
The server understood the request, but is refusing to fulfill it, possibly due to the permissions set for a particular file or directory. Authorization will not help and the request should not be repeated.
404 Not Found
The server has not found anything matching the requested URL.
405 Method Not Allowed
The method specified in the Request-Line is not allowed for the resource identified by the requested URL.
406 None Acceptable
The server has found a resource matching the Request-URI, but not one that satisfies the conditions identified by the Accept and Accept-Encoding request headers.
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. The client may repeat the request without modifications at any later time.
409 Conflict
The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user may be able to resolve the conflict and resubmit the request.
410 Gone
The requested resource is no longer available at the server and no forwarding address is known. This condition should be considered permanent.
411 Length Required
The server refuses to accept the request without a defined Content-Length.
412 Unless True
This response code allows the client to place arbitrary preconditions on the current resource metainformation (header field data) and thus prevent the requested method from being applied to a resource other than the one intended.

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. This may be due to a bug in a CGI program.
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. The implication is that this is a temporary condition which will be alleviated after some delay.
504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server it accessed in attempting to complete the request.