Actually all of antivirus compatible with firefox but some times one of them became incompatible, the antivirus support try to fix asap, you can ask bleepingcomputer.com forum about antivirus suggestion, but i suggest Upgrade your browser to Firefox 8

• getfirefox.com

I use AVG because its free and they have a firefox extension for it

AVG is one of the most populer anti virus you can get

I've used Symantec's Norton 360 for many years now and it works great overall. Personally, I stay away from free software, especially when it has to do with internet / PC security, though I do know some friends who use AVG.

You can get Norton 360 from online stores like Amazon or directly from Symantec online. I initially got mine from Amazon at a discount and then renewed it online annually. I just looked it up at Amazon and it's currently at a 57% discounted prices (as per the link above).

Norton 360 has a useful Firefox extension as well which securely stores passwords for various websites that one uses.

I am kaspersky lab gold beta tester and i use Kaspersky Internet Security

From my experience i recommend Avast (which I use at home) and Avira AntiVir (at work) - both free and good antivirus programs. Avast adds extension for rating sites as safe or not (like the WOT extension) Avira does not.

This program - the perfect solution for a simple user: antivirus that can protect against all threats at the highest level. http://theshhit.com/download-free/1-23513-AVG-Anti-Virus-plus-Firewall.html