This is something that stole a few minutes of my life this morning - I couldn't find a web proxy that worked with a site I'm developing in XHTML Strict:

Proxy web browser for XHTML Strict and non port-80 hosts

I must have tried more than a dozen that either failed to visit an IP address + port URL, or if they did they produced non-compliant XHTML output.

There's a link to a local source for an IP to Country database in the article too.

I hope this saves someone some time!

(seems like your preview CSS is all messed up again - do you need me to post a screenshot?)