"502 : That's an error" Details

"The server encountered a temporary error and could not complete your request.
Please try again in 30 seconds. That's all we know."
The above error propped up in my gmail account. And guess what they were back in 30 seconds.

But it might not be the case with all of us if the problem is in not in their servers.

502 error in a gist 

Poor IP communication with back end computers or the server of the website.

502 error for all the websites

• Internet Service Provider has a major equipment failure/overload  : only the ISP can fix the problem
• Internal Internet connection error like firewall which is preventing the access : Turn off the firewalls which is obstructing the connection

502 error for a particular website

• The error most probably points towards the server of the website.