Came across this on LifeHacker.com...
A 64-bit version of Firefox. If you use a 64-bit Operating System, and you should, then download Waterfox. Honestly, I can't tell any speed difference from any of the browsers, but some definitely display and have better plugins than others. Also, look better overall compared to others.
It uses the same directories as Firefox, so if you're currently a Firefox user as I am/was then you will have all your plugins, bookmarks, etc when you use Waterfox. I'm currently using Waterfox to post this also.
Here is the link to the LifeHacker article which links to Waterfox downloads... http://lifehacker.com/5871373/waterfox-is-a-faster-64+bit-optimized-version-of-firefox-for-windows-pcs