Reference: RFC 2616 - HTTP Status Code Definitions
- 400 BAD REQUEST: The request was invalid or cannot be otherwise served. An accompanying error message will explain further. For security reasons, requests without authentication are considered invalid and will yield this response.
- 401 UNAUTHORIZED: The authentication credentials are missing, or if supplied are not valid or not sufficient to access the resource.
- 403 FORBIDDEN: The request has been refused. See the accompanying message for the specific reason (most likely for exceeding rate limit).
- 404 NOT FOUND: The URI requested is invalid or the resource requested does not exists.
- 406 NOT ACCEPTABLE: The request specified an invalid format.