If you are a Mac G4 or G5 user then make sure you stop over to the download site below and pick up the optimized version of Firefox 220.127.116.11! This is a nice piece of work that will help Firefox run smoother on your Mac. With the popularity of Firefox (it has gained more than 10% of the market share) these builds should definitely appeal to those running a G4 or G5.
There are two versions that you can download, Firefox 18.104.22.168 and Firefox 2.0 Alpha. If you want to browse on the edge of your seat then Firefox 2.0 Alpha is the one that you want, however, it may not be very stable (especially since these are nightly builds). If you are not sure which one to get I recommend sticking with the Firefox 22.214.171.124.