5xx is the server error. Response status code beginning with '5' indicates cases in which the server is aware that it has encountered an error or is otherwise uncapable of performing the requesr.
500 (internal error) A generic error message, given with no more specific message i s suitable.
501( not implemented) - The server either does not recognise the request method or it lacks the ability to fulfill the request.
503 (service unavailible) - The server is currently unavilible because it might be overloaded or it is down with maintenance.
