Firefox has always had an outstanding position in the always competitive web browser battles. Firefox 9, though not very different from Firefox 8 in terms of design, brings a bunch of great improvements.
The most notable changes in Firefox 9 are the addition of Type Inference, significantly improving JavaScript performance, improved theme integration for Mac OS X Lion and the addition of two finger swipe navigation for Mac OS X Lion
The slight disadvantage of Firefox 9 is that many add-ons won't work from the start until the developers have upgraded them although the beta testing period for version 8 should have given them chance to do so. The interface in Firefox 8 is pretty much the same as Firefox 7, with a minimalist toolbar and hidden buttons.
Other than this, Firefox 9 mainly introduces improvements to memory usage and performance when having many tabs open. Firefox 9 is slightly more responsive and has some significant improvements to the JavaScript handling as well as improved support for HTML5 canvas, SMIL, MathML, and XHR. As a result, Firefox 9 is a little faster when loading pages.
Firefox 9 isn't a revolution in the development of Firefox, but there are some useful improvements that still make it a decent browser.
