Quote[/b] ]Firefox features the Gecko browser rendering technology that offers 100% W3C standards compliance and is constantly updated thanks to it being open source. It contains support for the latest web technologies including CSS2 and XHTML. Since it has no ActiveX support, there's no fear of any surreptitiously installed crapware on your machine. The browser has a far fewer number of bugs than Internet Explorer, making it even an more secure alternative. This is not to say that Firefox has no bugs, but the fact that its open source lets the entire community go through the cycle of detection, patching and release in an extremely short amount of time - as short as a few hours to one day. Firefox's built-in seamless automatic updates feature makes possible the adoption of new versions and/or patches.
The browser was also written to be easy to extend by writing plugins, known as extensions. With XUL programming, extension developers can modify Firefox anyhow they wish, be it a complete makeover by themes, or significant functional extensions. Out of the box, the browser doesn't support a huge list of features other than tabbed browsing and integrated download management, etc., however, the popularity of the extension model makes it the most versatile browser out there. Almost anything you want can be had in the form of an extension.