The Firefox Web browser has surpassed 100 million downloads just before celebrating its first birthday.

The Mozilla Foundation attributed the browser's success to its community of developers who have contributed code and features to the project, and the Spread Firefox community which develops, tests and markets Firefox.

Supporters of the browser say it is a more secure, innovative and feature-rich browser than Microsoft's dominant Internet Explorer. It has certainly been the first browser to eat away at Explorer's market share - now holding between seven and nine percent of the Web browser market.

But Firefox has not been without its troubles. A report by Symantec in September said it had more confirmed vulnerabilities than Explorer in the first six months of 2005. And earlier this week, AOL's Netscape division released an update to the Netscape browser that also fixes vulnerabilities in Firefox 1.0.7, released by Mozilla.

The first major Firefox upgrade, Version 1.5, is currently in beta testing and is expected to be generally available before the end of the year. At the same time, Microsoft is working on a major Explorer upgrade, also in beta testing. Internet Explorer 7 will be included in Windows Vista, which is scheduled for late 2006.