I don’t know this for sure and surley Opera has not paid me to do this but for some odd reason or the other more and more people are turning to Firefox for their web browser. Personally I hate the stupid plug-ins for Firefox. A true browser should have all those features already enabled in it, out of the box. So the best alternative is Opera. It is awsome and I have been using it for the past eight years, from version 3 (its now version 8). It is the best browser I have ever used. It is very fast because of its own independent web page rendering engine. It was, however, paid at first but now its free, a perfect reason to download it. It is only about 8-9 Mb and has all the features of Firefox and IE combined. I would highly recommend it to anyone devoted to the internet (like I am).
You can get it free at http://www.opera.com