Blocking the ad pages also prevents them from getting info about your browsing habits. Another bonus.
I feel behind the curve, not having used this plug in before.
You should be using the REFCONTROL 0.8.11 add on. You can set the url referrer address to anything you like, such as http//www.Obama-is-a-Marxist-commie.com. ;)
http://www.torproject.org/
You can use “Hostal” (for the Macintosh), too...
http://www.apple.com/downloads/macosx/internet_utilities/hostal.html
It’s a little program that makes it easy for you to handle and manipulate a “hosts” file on your computer... (and this will block web addresses and sites and ads and so on...).
Hosts file
http://en.wikipedia.org/wiki/Hosts_file