Wow, that was fast, right? It was only 90 days ago that Mozilla debuted Firefox 4 and those nuts have already gone ahead and jumped forward another full version number. So what’s changed in those three months? Mostly some under the hood stuff, so read on.

Mozilla announced the availability of Firefox 5 on Tuesday, which was likely lost on many Mac users who were busy downloading Apple’s new Final Cut Pro X and companion apps Motion 5 and Compressor 4. While Firefox 5 isn’t as radical a change as Firefox 4 was when it was released all of three months ago, the new version gains a lot of improvements where it counts, which is under the hood.

Among the Firefox 5 new features are support for CSS animations, a new place for the Do-Not-Track header preference “to increase discoverability” (i.e., nobody could find it before, apparently) and “tuned HTTP idle connection logic for increased performance.”

But that’s not all -- heavens, no! Firefox 5 makes a ton of improvements across the board, with canvas, JavaScript, memory and networking performance, improved standards support for HTML5, XHR, MathML, SMIL and canvas, improved spell checking “for some locales” and Linux users get a bonus with improved desktop environment integration.

We know, none of that seems to warrant a full version number release in such a short time, but those kooky kids at Mozilla are really stepping up their game and plan to keep pumping out the updates at a rapid clip. Somebody’s got to keep up with Google Chrome, right?

Head over to the Mozilla website and download Firefox 5 today -- if you haven’t installed Firefox 4 yet, it will be like a whole new experience for you.

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