Mac i was getting party poker and all sorts of full page adds etc after i reformatted and before i edited and added the forementioned Hosts File...once i added the list to my file they stopped completely...
The Hosts File given on that page blocks ads/banners etc as well as the third party cookies that throw up the adds that come up without URLs.
If you're not comfortable using the file download try this free app from MajorGeeks...see if it works for you.
http://majorgeeks.com/download2859.html