New beta paves way for Firefox 3.5

Updated 3:56 p.m. PDT to include details about the fourth beta and upcoming Firefox 3.5

Mozilla on Thursday released the third beta version of Firefox 3.1, aka Shiretoko, one of the frontrunners in the current race to improve Web browsers.

According to the Firefox 3.1b3 release notes, the new version includes better "Web worker" multitasking abilities, a faster Gecko rendering engine for showing Web pages, and upgrades to the TraceMonkey engine for faster, more stable execution of Web sites' JavaScript programs. (Follow these links to download Firefox 3.1b3 for Windows and Mac OS X.)

Firefox is vying with Apple's Safari 4 beta and Google's Chrome for the best JavaScript performance, a factor that's important for the new generation of sophisticated Web sites such as Google Docs and or Facebook applications. So far, Internet Explorer has the dominant market share, with Firefox in second place.

Mozilla earlier expected the third beta version to be the final beta, but those plans changed. Because of the magnitude of the changes in the 3.1 betas, the next full release will be numbered 3.5. A fourth beta, 3.5b4 is planned, too, followed by the release-candidate cycle, before the final version 3.5 is released, Mozilla said.

"The increase in version number is proposed due to the sheer volume of work which makes Shiretoko feel like much more than a small, incremental improvement over Firefox 3: TraceMonkey, video tag and player support, improvements to user controls over data privacy, significant improvements in the web layout and rendering platform, and much more," said Mozilla's Mike Beltzner in a blog post last week.

Here's Mozilla's full list of improvements in the new beta:

• Improved the new Private Browsing Mode.

• Improvements to Web worker thread support.

• Improved performance and stability with the new TraceMonkey JavaScript engine.

• New native JSON support.

• Improvements to the Gecko layout engine, including speculative parsing for faster content rendering.

• Support for new Web technologies such as the video and audio elements, the W3C Geolocation API, JavaScript query selectors, CSS 2.1 and 3 properties, SVG transforms and offline applications.

Web workers let a browser perform computing tasks in the background, which allows for more sophisticated programs. JSON, or JavaScript Object Notation, lets a browser and a server share information, and Mozilla argues that building it natively into the browser improves speed and security. Private browsing is built into Chrome and Safari, and Mozilla felt the peer pressure. Built-in-video and audio support means that no Flash player or other technology is required--but it only works today with the relatively rare Ogg file formats.

It's a beta, and there are problems such as an issue where Gmail hangs, so be careful about installing it.