HTTP Status Codes

200 (OK) This code indicates the request was successful. For GET requests, the body of a 200 response contains the entire object requested.
201 (Created) This code informs the client that its request resulted in the successful creation of a new resource, which can now be referenced.
203 (Non-Authoritative Information) This code may be used in place of 200 when the sender has reason to believe the information in the response's entity headers are different than what the origin server would send.
204 (No Content) This code is used in cases where the request was successfully processed, but the response doesn't have a message body.
400 (Bad Request) This code indicates that the server could not understand the client's request, or found it to be incorrect in some way.
401 (Unauthorized) This code is used when access to a resource is protected and the client did not provide valid authentication credentials. Often the 401 response includes information that causes the user agent to prompt the user for a username and password.
403 (Forbidden) This code indicates that the resource cannot be accessed, regardless of any authentication credentials. For example, this happens if a directory or file is unreadable due to file permissions.
404 (Not Found) This code indicates that the requested resource does not exist on the server. It may also be used in place of 403 if the server doesn't want to acknowledge that the resource exists, but cannot be accessed.
405 (Method Not Allowed) This code indicates that the request method is inappropriate for the given URI. The response should include a list of methods that are allowed.