502 Error Message

[#1]

I'm finding my connection very slow this morning and on a few sites i am trying I am getting the following 502 error message:
Proxy Error
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /uk/.
Reason: Error reading from remote server
Is there a problem?

[#2]

Since my earlier post the problem seems to have resolved itself.  I would be interested to know what the error message was about though.  Thanks.

[#3]

Quote from: artmo

Since my earlier post the problem seems to have resolved itself.  I would be interested to know what the error message was about though.  Thanks.

And I quote....  !
Fixing 502 errors - general
This problem is due to poor IP communication between back-end computers, possibly including the Web server at the site you are trying to visit. Before analysing this problem, you should clear your browser cache completely.
If you are surfing the Web and see this problem for all Web sites you try to 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 get this problem for only some of the Web sites you try to visit then it is likely to be a problem at those sites i.e. one of their pieces of equipment is failing/overloaded. Contact the people at those sites.

[#4]

Thanks nozzer that is useful.  The error came up on odd sites and seems to have cleared itself now although I have noticed browsing has been crawling today.