martinibuster - 7:59 pm on Apr 2, 2013 (gmt 0)
Sounds like you've been hacked. Check the source code of the web page to identify what part of the page the rogue code is on. Once you know that then you can track down what template file may have been altered and then you can revert it back to it's previous state. Some of these hackings consist of code placed within an iFrame.
This is a temporary fix but if you do it fast enough you may avoid a larger problem, namely being blacklisted by Google/McAfee/Norton as being malware spewing infested website. THEN you'll really have trouble as your traffic dries up to zero. Even worse, once you fixed it you will then have to go around to all the companies that banned you and get your site off their blacklists.
Don't wait for those admins to get back to you. It's likely that it's your site that's the problem and they rarely get involved other than turning you off if they're nice and kicking you off if they're not. Fix it, and fix it fast.
As I mentioned previously, this is a temporary fix. The hackers will be back and will re-hack it. So fix it, patch up your software, patch up or remove any mods that might be the source of the exploit.
It could be worse. They could have trashed your database and made it irrecoverable.
Are you running VBSEO? VBSEO has a history of getting hacked. Do a search for VBSEO + hacked and you'll see what I mean.