Full Review

Although Firefox 3.6 isn't as ambitious an update as Firefox 3.5 was, it includes a number of under-the-hood improvements and a handful of visible changes.

Firefox 3.6 can now detect whether any of your installed browser plugins are out of date. Cyber-criminals often use bugs in outdated versions of some browser plugins--particularly Flash and QuickTime--to attack your PC and potentially install malware that can be used to steal your personal information, or turn your PC into a spam bot. In essence, Firefox 3.6 now automatically does what Mozilla's Plugin Check page did for earlier versions of Firefox.

The most visually noticeable change is support for Firefox Personas. Personas are basically interface skins you can apply with one click.

You can now watch certain types of videos in full screen with Firefox 3.6. If the video is in the Ogg Vorbis format, you can right-click the video and select an option to see it in full-screen. The downside to this feature is that it works only with certain video formats.

When we last tested browser page loading speed, we found that Firefox 3.5 was a good deal faster than earlier Firefox versions. Mozilla claims that Firefox 3.6 is even faster, with improvements to JavaScript performance in particular, which should result in faster load times for Web pages and Web apps. Firefox also improves support for some of the latest Web design technologies, which should make it easier for designers to create better, more attractive sites.

Perhaps as a sign of things to come, if your notebook or tablet has an accelerometer that detects changes in orientation, Firefox 3.6 will now be able to tell. When you rotate your gadget, it'll rotate with it.

The most visually noticeable change is support for Firefox Personas. Personas are basically interface skins you can apply with one click. They're similar to the skins available for the Google Chrome browser. Mozilla's gallery of personas at getpersonas.com features over 35,000 designs.

Applying a Persona is easy: Visit the Personas gallery using Firefox 3.6. To "try on" a Persona, mouse over it; Firefox will temporarily change its appearance to that Persona. If you like it, click it. If you decide to revert to the default theme, select Add-ons from the Tools menu, click Themes, then select Default.

We noticed that many themes look better on the Windows version than on the Mac version; it appears that Personas were designed to take the Windows titlebar into account, but not the "unified" look of a Firefox window on Mac OS X (where the toolbar and titlebar appear to be one). Also, Personas won't necessarily boost productivity; some of the ones we tried make the text in the toolbar difficult to read.

If you use Firefox 3.5, upgrading to 3.6 is a no-brainer. And if you use an earlier version, you too should upgrade, if for no other reason than to avoid any known security flaws that might affect older versions.