Firefox Portable 3.6.11
No longer a fledgling upstart, Firefox 3 is full-featured, lightning fast, and an able foe for both the big-dog competitor Internet Explorer and competitors nipping at its heels. Firefox's killer add-ons remain strong, and the latest update makes version 3.5 about two times faster than version 3. However, competition is strong and it can no longer be said that Firefox is the fastest browser available.
Web developers should be excited about expanded support for HTML5 local storage, downloadable fonts, and native support for OGG-formatted embedded video. ICC profiles, SVG transforms, CSS media queries, native JSON support, and Web worker threads also get lots of love from v3.5. There's no doubt that Firefox 3.5 is a must-have, but it's an update that's more about keeping the browser current rather that blazing new trails.