HTTP CODES 500-505

500 - Internal Server Error
The request was unsuccessful due to an unexpected condition encountered by the server.

501 - Not Implemented
The request was unsuccessful because the server can not support the functionality needed to fulfill the request.

502 - Bad Gateway
The server received an invalid response from the upstream server while trying to fulfill the request.

503 - Service Unavailable
The request was unsuccessful to the server being down or overloaded.

504 - Gateway Timeout
The upstream server failed to send a request in the time allowed by the server.

505 - HTTP Version Not Supported
The server does not support or is not allowing the HTTP protocol version specified in the request.