HTTP 1.0 response codes

Response code	Meaning
2xx Successful	Response codes between 200 and 299 indicate that the request was received, understood, and accepted.
200 OK	This is the most common response code. If the request used GET or POST, the requested data is contained in the response along with the usual headers. If the request used HEAD, only the header information is included.
201 Created	The server has created a data file at a URL specified in the body of the response. The web browser should now attempt to load that URL. This is sent only in response to POST requests.
202 Accepted	This rather uncommon response indicates that a request (generally from POST) is being processed, but the processing is not yet complete so no response can be returned. The server should return an HTML page that explains the situation to the user, provides an estimate of when the request is likely to be completed, and, ideally, has a link to a status monitor of some kind.
204 No Content	The server has successfully processed the request but has no information to send back to the client. This is usually the result of a poorly written form-processing program that accepts data but does not return a response to the user indicating that it has finished.
3xx Redirection	Response codes from 300 to 399 indicate that the web browser needs to go to a different page.
300 Multiple Choices	The page requested is available from one or more locations. The body of the response includes a list of locations from which the user or web browser can pick the most appropriate one. If the server prefers one of these locations, the URL of this choice is included in a Location header, which web browsers can use to load the preferred page.
301 Moved Permanently	The page has moved to a new URL. The web browser should automatically load the page at this URL and update any bookmarks that point to the old URL.
302 Moved Temporarily	This unusual response code indicates that a page is temporarily at a new URL but that the document's location will change again in the foreseeable future, so bookmarks should not be updated.
304 Not Modified	The client has performed a GET request but used the If-Modified-Since header to indicate that it wants the document only if it has been recently updated. This status code is returned because the document has not been updated. The web browser will now load the page from a cache.
4xx Client Error	Response codes from 400 to 499 indicate that the client has erred in some fashion, although the error may as easily be the result of an unreliable network connection as of a buggy or nonconforming web browser. The browser should stop sending data to the server as soon as it receives a 4xx response. Unless it is responding to a HEAD request, the server should explain the error status in the body of its response.
400 Bad Request	The client request to the server used improper syntax. This is rather unusual, although it is likely to happen if you're writing and debugging a client.
401 Unauthorized	Authorization, generally username and password controlled, is required to access this page. Either the username and password have not yet been presented or the username and password are invalid.
403 Forbidden	The server understood the request but is deliberately refusing to process it. Authorization will not help. One reason this occurs is that the client asks for a directory listing but the server is not configured to provide it, as shown in Figure 3-1.
404 Not Found	This most common error response indicates that the server cannot find the requested page. It may indicate a bad link, a page that has moved with no forwarding address, a mistyped URL, or something similar.
5xx Server Error	Response codes from 500 to 599 indicate that something has gone wrong with the server, and the server cannot fix the problem.
500 Internal Server Error	An unexpected condition occurred that the server does not know how to handle.
501 Not Implemented	The server does not have the feature that is needed to fulfill this request. A server that cannot handle POST requests might send this response to a client that tried to POST form data to it.
502 Bad Gateway	This response is applicable only to servers that act as proxies or gateways. It indicates that the proxy received an invalid response from a server it was connecting to in an effort to fulfill the request.
503 Service Unavailable	The server is temporarily unable to handle the request, perhaps as a result of overloading or maintenance.