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Background: Trying to chase a bug where resources occasionally won't load. Only happens on mobile devices.

Last five columns in IIS logs are cs(User-Agent) sc-status sc-substatus sc-win32-status time-taken

What I don't understand is we have entries like: {..user agent..} 590 0 0 15

If we map it, appears that some images return HTTP "590". Is there such a thing? I'm probably missing something here, any ideas?

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User agent 590 is different from an http return code of 590. But, for what it's worth, the only 59x http codes I'm aware of are 598 and 599, Network read timeout error (Unknown) and Network connect timeout error (Unknown), respectively. The fact that it only happens on mobile devices, and those error codes would make me suspect wireless connectivity issues, but that's all I've got. – HopelessN00b Dec 12 '12 at 14:42
Thanks for the info. It's not in the UA but in the sc-status column, which really bothers me because we all know there is no such kind of code. – Neps Dec 12 '12 at 20:34

Just found out that the server was configured with an error page which outputs this "custom" status code.

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