Firefox is a free, multiplatform browser. Its popularity is second only to Microsoft's Internet Explorer among Web browsers, but unlike IE, it has open-source code. The result has been an avid development community, filled with people eager to squash bugs and create new functionality. Firefox also has the option to create and use extensions that can add new features or services right on top of the user experience. These add-ons have gotten so popular that Firefox creator Mozilla has created its own directory for users to search and sort through them.
2008 was the year of Firefox 3, which sports an updated look and an updated rendering engine that's several times faster than the one that came before it. Over 8 million copies of the software were downloaded in a 24-hour period in late June as part of Firefox's download day celebration. In 2009 the company continues to push out further revisions that fix bugs and add new features.