Hmm you are still here...
...perhaps you are looking for HTTP status codes?
400 Bad Request
The server cannot or will not process the request due to an apparent client error.
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402 Payment Required
Reserved for future use. The original intention was that this code might be used as part of some form of digital cash or micropayment scheme, but that has not happened.
The request was valid, but the server is refusing action. The user might not have the necessary permissions for a resource.
404 Not Found
The requested resource could not be found but may be available in the future. Subsequent requests by the client are permissible.
405 Method Not Allowed
A request method is not supported for the requested resource; for example, a GET request on a form that requires data to be presented via POST.