Mozilla Firefox is a web browser project descended from the Mozilla application suite, managed by the Mozilla Corporation. Firefox had 16.01% of the recorded market share in Web browsers as of November 2007, making it the second-most-popular browser in current use worldwide. Firefox uses the open-source Gecko layout engine, which implements 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 includes 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 and Linux. Its current stable release is version 2.0.0.11, released on 30 November 2007. Firefox's source code is under the terms of the Mozilla tri-license as free and open source software.