When websites are called up using the HTTP protocol, the client, i.e. the web browser, sends a request to the server using the request-responseprocedure. The server responds with a response that always contains an HTTP status code.
This status code also indicates faulty page requests and error pages, i.e. server errors. The error pages due to the client have the HTTP status code 4xx, those due to the server have 5xx.
Unexpected server errors are indicated with the collective status code 500. In addition to the collective status code 500, there are various other status codes for Server Errors. For example, 501 indicates an unimplemented function not provided by the server, 502 an unimplemented gateway function of the web server, 503 an unavailable server, 504 no server response in a certain period of time, 505 an unsupported http version, 506 no reference of the content specification, 507 insufficient storage capacity, 509 to low bandwidth, and 510 an incomplete request.