Well now it might be. You can block ads by using AdBlock extension for Firefox.
Block list for AdBlock can be found on my eXcessive Software page found in my signature.
For me,AdBlock is probably the one and main reason to use Firefox. It's just so damn good
Otherwise i'd probably use Opera hehe
Just load the block list to AdBlock extension and say goodby to ad banners and other crap on webpages.
WebWasher is ok,but not nearly as flexible and effective as AdBlock.