Firefox 3 delivers an impressive assortment of new features and interface improvements. There are lots of changes under the hood as well, which improve performance and reduce resource consumption. Firefox 3 is built on top of Gecko 1.9, the new version of Firefox's HTML rendering engine. In Gecko 1.9, much of the underlying rendering code is now performed with Cairo, an open source vector graphics software library that can leverage hardware accelerated rendering. As we have previously reported, the Gecko 1.9 rendering engine can pass the Acid 2 test, a CSS test case developed by the Web Standards Project. Several impressive additions to Firefox 3 were made possible by the Gecko overhaul, including support for full-page zoom.
Overall Firefox 3 seems to offer quite a bit of improvements for the end-user.