FAQ - What programs can I use with Tor? - outdated
Most of our work so far has focused on the Firefox web browser. The bundles on the download page automatically install the Torbutton Firefox extension if you have Firefox installed. As of version 1.2.0, Torbutton now takes care of a lot of the connection-level and application-level worries.
You don't install TorButton anymore. You install a bundle optimized for anonymity and privacy with a patched variant of Firefox. Installing TorButton manually in stock Firefox is discouraged. That FAQ entry should reflect that.