504 Error Code Explained
The server was acting as a gateway or proxy and did not receive a timely request from the upstream server.
Why it occurs
A 504 status code is returned when a server acting as a proxy has waited too long for a response from a server further upstream.The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.
Fixing 504 error code
This problem can be fixed only by the people who set up the network at the site which hosts the Web server
If you are registered with 100pulse, your site will be monitored and you will be intimated by an email or a short message service when 504 status code error occurs.