As a computer Junkie for more than 20 years I would not recommend the addition to the hosts file that is posted here. 127.0.0.1 is the internal IP address for yourself and naming it "media.fastclick.net" seams like a bad idea to me. You are in effect confusing your IP Stack into thinking that you are called "media.fastclick.net" There are ways to block the popups without compromising your own security. I would not do this, and My recommendation would be to investigate this kind of thing thoroughly