Mozilla released a third beta of Firefox 3.6 on Wednesday, adding stability and performance features, and said it hopes to lock down the code soon for its first release candidate.

The new beta, for Windows, Mac, and Linux, includes a component directory lockdown that makes it harder for other software to meddle with the open-source browser's state by preventing that software from sidling into the same folder as the browser's own components. The result should be fewer crashes, said Mozilla's Johnathan Nightingale in a blog post, and Firefox still is open to third-party extensions via its official add-on mechanism.

The change should improve security, too, added another Mozilla programmer, Vladimir Vukecevic, who wrote in his own blog post that Mozilla is considering bringing the change to Firefox 3.5, too.

"Creating binary components to interface with the operating system or with other applications is fairly straightforward, though ultimately dangerous. Binary components have full access to the application and OS, and so can impact stability, security, and performance," Vukecevic said.

Also in the latest beta of 3.6 is a feature that lets the browser run some Web-based JavaScript programs asynchronously, which is to say without being so picky about the order the scripts run. This can improve the speed that Web pages load, Mozilla said.

The biggest Firefox 3.6 feature most folks will notice is Personas, the reskinning add-on that's now being built in. More than 10 million Personas have been downloaded so far, Suneel Gupta and Myk Melez of the Personas team said Wednesday.

Mozilla is working to release a final version of Firefox 3.6 before the end of the year, and one sign the project is wrapping up is that the developers are locking down the features and changes that can be added into the release candidate 1. Code freeze for RC1 is scheduled for Wednesday but might be at risk, a Mozilla planning site said this week.

Firefox is steadily gaining in use. Last week, Web traffic monitoring firm Net Applications announced Firefox cleared 25 percent share of those using browsers worldwide--not dethroning Internet Explorer by any means but still winning over new users. Mozilla estimates there are more than 300 million Firefox users total, and this week said there are more than 300,000 testers using the Firefox 3.6 beta

Google's Chrome, meanwhile, is appealing to some of the same browser enthusiasts who were Firefox's first users. One of its big selling points is speed, and Google is working on other ways to make the Web faster, too. Chrome gives it a vehicle to test such ideas out in the real world, a strategy that Apple, Opera, and Firefox have employed to advance the Web state of the art.

One Mozilla programmer, Alexander Limi, revealed a speedup technology called Resource Package for Mozilla, too, on Tuesday. His proposal calls for bundling many Web page elements up into a single compressed file that can be retrieved in a single Web-page request action. Browsers are limited in the number of such actions they can take in parallel, so consolidating the interactions can make pages load faster. The approach is backwards compatible with existing browsers that don't support the feature, he added.

"If the feedback is good we're likely to try and get this implemented for Firefox 3.7," said Mozilla evangelist Christopher Blizzard in a blog post Tuesday.