A post on the Blizzard forums to be careful visiting WoWhead.
http://us.battle.net/forums/en/wow/topic/20752227502

I suppose the site could have been hacked, but seems to me its been like this for awhile. Constant page reloads, dozens and dozens of ads, even malware ads.

WoW is getting more popular worldwide, but its less popular in the US and I think wowhead is just trying to milk as much as they can while they can.