just did a search and found this review of Firefox...(in case you 'viri' infected folks don't want to look, it includes these words...)

" Even though I had left the computers hooked up on a high-speed Internet connection almost daily for periods of up to eight hours at a time, often unattended but also with a good deal of Web activity thrown in, I had no spyware or viruses to report on the laptop. The computer with Internet Explorer, however, had about 14 instances of spyware.

The absence of viruses or spyware on the Firefox computer says a lot, as a machine with that type of Internet connection using a virus-prone operating system is almost unheard of.

and adds "Firefox is available, though. Tested and proven, it can help keep your computer system clean of spyware as well as some common, nasty viruses. But remember, Firefox is not totally immune, and it is still necessary for you to take precautions to protect your system — including the use of a firewall."