HTTP Error Response codes

Error code	Description
400 Bad Request	Request did not contain a host to connect to or if there was a generic error when validating a request.
403 Forbidden	Error when validating ACL for request.
407 Proxy Authentification Required	Request lacks proxy authentication information, or username or password is invalid.
429 Hard limit reached	Hard limit value reached, sending additional IP requests is blocked.
500 Internal server error	Proxy server has encountered an internal error.
502 Bad Gateway	Error when request proxying encountered an error.
504 Timeout	A proxy server did not receive a response from the upstream server in time. Try again.
525 Exit node missing	Error shown when no exit node was found to complete the request.