Microsoft&39's IE team congratulates Mozilla on every Firefox release with a cake. Here&39's the cake, complete with the updated IE9 logo, for Firefox 5. &34'We have streamlined our cake release process to keep up with Mozilla&39's schedule,&34' quipped Microsoft&39's Sylvain Galineau about the cake.

Mozilla delivered two things today: Firefox 5 for personal computers and Android phones, and the promise to complete the new browser just a few months after its predecessor.

The organization, once the leading challenger to Microsoft's Internet Explorer, faces new challenges--notably Google's Chrome, new versions of which arrive every six weeks. Adopting a similar philosophy, Firefox now revs on a three-month cycle, and today Mozilla met its first deadline.

"The world of the Internet is moving at a faster pace than ever, so we realized we had to start innovating faster," said Mozilla Chief Executive Gary Kovacs in an online chat today to announce the product.

New features in Firefox 5 (download for Windows | Mac | Linux | Android) include the following:

&149' Support for CSS animations, a technology that lets Web page elements move around the screen. That's useful for more dynamic Web pages and Web apps.

&149' Firefox's new Add-on SDK, formerly called Jetpack. This foundation lets programmers build extensions out of Web technologies such as HTML, CSS, and JavaScript rather than the older XUL technology. The expected advantages: extensions will be easier to write and won't break when new browser versions arrive.

&149' In beta testing is the Add-on Builder, a Web-based tool designed to make writing extensions easier.

&149' Firefox's do-not-track technology, which lets people tell Web sites they don't want to be tracked for advertising or other purposes, now works on Android phones as well.

&149' Canvas, which adds two-dimensional graphics technology to browsers, runs faster now, and adheres better to the official specification.

Firefox 5 gives the do-not-track preference more prominence.

&149' Mozilla worked on performance in various other areas, including JavaScript and launch time.

&149' On Android, Firefox 5 now supports the Web Open Font Format for downloadable typefaces to embellish Web pages.

&149' Also on Android, panning around a Web page should be smoother.

Firefox 4 was a major overhaul to the open-source browser, and Mozilla said it was downloaded more than 200 million times for personal computers and Android phones. The faster cycle means new releases aren't as dramatically different from their earlier counterparts, though.

"Firefox 6, 7, 8, 9, 10--they're every bit as important, but they won't have this massive celebration," Kovacs said. "They'll just be part of how we deliver awesomeness to the Web."

In addition to the final release version of Firefox, Mozilla has added two faster-moving test versions, the beta version and the Aurora version for the more adventurous. (There's also a nightly version for those on the bleeding edge.)

One consequence of the faster cycle is of course that developers have to move quickly to catch the next release "train." Another, though, is that another train comes in another six weeks. That makes it easier to maintain the release schedule discipline, said Christian Legnitto, Mozilla's Firefox release manager.

"We were a little worried about the transition," he said, but the new schedule worked. "It's been amazing watching the project do an about-face."

Updated at 2:21 p.m. PT with IE cake from Microsoft and a little more detail.