502 Error Code Explained
The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in the attempt to fulfill the request.
Why it occurs
A server is acting as a gateway or proxy to fulfil the request by the client ,to access the requested URL. The error occurs When this server receives an invalid response from an upstream server it accessed to fulfil the request.
This usually does not mean that the upstream server is down , but rather that the upstream server and the gateway/proxy do not agree on the protocol for exchanging data.
Fixing 502 error code
Both the proxy and upstream server should be programmed correctly and completely.The IP communication between back-end computers should be good.Before analysing this problem, you should clear your browser cache completely.If you see this problem for all the sites you visit,then either 1) your ISP has a major equipment failure/overload or 2) there is something wrong with your internal Internet connection e.g. your firewall is not functioning correctly. In the first case, only your ISP can help you. In the second case, you need to fix whatever it is that is preventing you reaching the Internet.
If you have been registered with 100pulse, your site will be monitored and you will be intimated by an email or a short message service when 502 status code error occurs.