EDIT: I also like http://neverssl.com which has no TLS defined which is handy to trigger finicky network login screens.
That's your first point of troubleshooting anytime you're on a new network and aren't certain whether a problem you're seeing is due to some kind of tampering proxy or configuration policy.
EDIT: I also like http://neverssl.com which has no TLS defined which is handy to trigger finicky network login screens.