The above are true but the last couple days have been "Woot Offs" where they sell out the items they have just a few left of the built up over the past month or so. During a "Woot Off" the item may be available for a short time, sometime only a few minutes even.
But in any case if you click on the "Buy" link and it's a different item that deal is over.
Also I recently added all the woot sites to the thread. woot.com is the original. But there is also now sellout.woot, kids.woot, home.woot, wine.woot, and shirt.woot- all of which usually sell 1 item a day but occasionally have woot-offs.