5xx family (server error)

These are the errors from the server. The client request may be perfect, but due to a bug in the server code, these errors can arise. The commonly used status codes are 500, 501, 502, 503,  and 504:

• 500 (Internal Server Error) status code gives the development error which is caused by some buggy code or some unexpected condition
• 501 (Not Implemented) is returned when the server is no longer supporting the method on a resource
• 502 (Bad Gateway) is returned when the server itself got an error response from another service vendor
• 503 (Service Unavailable) is returned when the server is down due to multiple reasons, like a heavy load or for maintenance
• 504 (Gateway Timeout) is returned when the server is waiting a long time for a response from another vendor and is taking too much time to serve the client

For more details on status codes, visit this link: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status