Mozilla Firefox is a web browser descended from the Mozilla Application Suite, managed by the Mozilla Corporation. Firefox had about 15% of the recorded usage share of Web browsers as of January 2008 making Firefox the second-most popular browser in current use worldwide after Internet Explorer.
Firefox uses the open-source Gecko layout engine, which implements some current Web standards plus a few features which are intended to anticipate likely additions to the standards.
Firefox includes tabbed browsing, a spell checker, incremental find, live bookmarking, a download manager, and a search system that uses Google. Functions can be added through more than 2,000 add-ons created by third party developers; the most popular include FoxyTunes (controls music players), Adblock Plus (ad blocker), StumbleUpon (website discovery), DownThemAll! (download functions) and Web Developer (web tools).
Firefox runs on various versions of Microsoft Windows, Mac OS X, Linux, and many other Unix-like operating systems. Firefox's source code is free software, released under a tri-license GPL/LGPL/MPL.
from wikipedia