401 Unauthorized

The request requires user authentication. The response MUST include a WWW-Authenticate header field (section 14.47) containing a challenge applicable to the requested resource. The client MAY repeat the request with a suitable Authorization header field (section 14.8). If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has already attempted authentication at least once, then the user SHOULD be presented the entity that was given in the response, since that entity might include relevant diagnostic information. HTTP access authentication is explained in "HTTP Authentication: Basic and Digest Access Authentication" [43].



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.



412 
Precondition Failed: Die in einem oder mehreren Anfrage Headern gegebenen Bedingungen wurden beim testen auf dem Server als falsch oder nicht erfüllbar eingestuft. Dieser Antwortcode erlaubt es dem Client anhand der Metainformationen der aktuellen Ressource Bedingungen zu stellen und dadurch die Anfragemethode vor der Anwendung auf eine falsche Ressource zu beschützen.