You'll want to be a bit more cautious when looking up information on the game today. World of Raids reports that an unknown ad banner appearing on Wowhead, Thottbot, and Allakhazam has an embedded
keylogger trojan. You don't even need to click on the banner, apparently, simply mousing over it will be enough. Wowhead says that all they know for sure is that it originates from "ad.yieldmanager.com", and will produce a redirect to "xpantivirus.com." They're working at isolating it.
The issue is known, and all parties involved are tracking it down, so it should hopefully be resolved soon. In the meantime, if you're looking for a quick way to protect yourself, I would follow the recommendation of World of Raids, and try out the Firefox web browser and the No Script extension. As long as you keep the scripts blocked, it should prevent the banner in question from forcing itself on you. This should also provide you with some protection if you accidentally click on the wrong link elsewhere, such as on the WoW general forums.
Edit: Apparently, the virus in question is not an actual keylogger, but it still does a number on your system, which is reason enough to try to avoid it.