Firefox, the top open source Web browser, celebrated its first birthday last week. Since the first production version of Firefox was launched Nov. 9, 2004, the Web browser has garnered around 7.6% of the Web browser market (according to market watcher Net Applications) compared to Microsoft's 87% of the market with Internet Explorer. Netscape, owned by AOL, has around 2% of the market. Firefox, according to Mozilla, has been downloaded over 100 million times.

Firefox is one of open source's greatest success stories in recent years. The software, which is distributed free, as well as the source code available under the Mozilla Public License, and is maintained by the non-profit Mozilla Foundation, as well as a worldwide community of open source developers and enthusiasts. Firefox is widely used by Windows users, as well as Linux and Mac machines. According to a survey by Desktoplinux.com, Firefox was the most popular browser among Linux desktop users, second only to its cousin, the Mozilla browser, on which the Firefox code is based.

Part of the big appeal of Firefox is extensions: little bits of code that add functionality or security to the browser. Popular ones include download managing extensions, script and pop-up blockers, and search and information tools. As part of Firefox's birthday, the Mozilla.org is promoting its Extend Firefox contest, which encourages hackers (the good kind) to come up with new extensions for the Web browser, which will be included in the forthcoming Version 1.5, due later this year.