The 502 Bad Gateway error is an HTTP status code that means that one server received an invalid response from another server.
The Bad Gateway error can be customized by each website. While fairly uncommon, different web servers do describe this error differently. Here are some common ways you might see it.
How the 502 Error Appears
"502 Bad Gateway"
"502 Service Temporarily Overloaded"
"Error 502"
"Temporary Error (502)"
"502 Proxy Error"
"502 Server Error: The server encountered a temporary error and could not complete your request"
"HTTP 502"
"502. That's an error"
"Bad Gateway: The proxy server received an invalid response from an upstream server"
"HTTP Error 502 - Bad Gateway"