Okay. I am using firefox too and I
almost never see ads. I have
Adblock and
NoScript which block all the ads and pop-ups I think. Try them and see if they help. You will have to build up a list of filters in Adblock to get it to block most ads. I can give you my list if you need them. You can use "*" as a wildcard. eg:
http://rad.msn.com/* (removes all ads in hotmail)