Firefox was a fork of the Navigator project. The first major release was on November 9, 2004. On that day, Firefox 1.0 was released.
In it’s first 99 days, Firefox 1.0 had over 25 million downloads. It became popular for it’s light weight interface, tabbed browsing, and abundant sources of extensions.
On the development side, Firefox’s open source code has allowed an increased compliance with many industry standards. It also has many developer extensions that allow much more rapid development of web applications.
Firefox 2.0 is a major milestone. The web browser has added features including new phishing filter technology, ability to open recently closed tabs, inline spell checking (very useful), support for next generation image files (Scalable Vector Graphics ), among other things.