What is Gmail’s 502 Error
You will get 502 error while signing into your gmail Account.(Of course not to every one and not every time).If you get this temporary error while signing into your account, it is due to Server problem.You will get this message when your mail is temporarily unavailable.It will set back to normal automatically. Gmail 502 Error:The Server encountered a temporary error and could not complete your request.Please Try Again in 30 Seconds.Message displayed by Google for 502 error.
Google’s help page describes, 502 error as “Temporary Error” message when you try to sign in to Gmail.These errors generally resolve themselves within a few minutes, so please wait a bit before trying to log in again.
So when you encountered this error “Leave gmail for few minutes” and try again.