The Steam User's Forums are temporarily offline for maintenance after hacker group Fkn0wned breached the website and put up ads for their own exploit website. We don't promote the use of hacking here at G4, but for informational purposes Fkn0wned's forums features hacks, a general discussion section, as well hacking tutorials and tools, porn, and more.
As of this writing, Valve hasn't commented on whether or not user details or Steam accounts have been compromised which is probably a good thing. The Fkn0wned team did send out a mass e-mail to Steam users letting them know to go to their website though. I'd personally advise against it.
When the Steam forums are back up we'll be sure to update this post and let you know.