Mozilla on Tuesday released its third beta version of Firefox 3.6, the latest edition of the company's popular open source Web browser.

Firefox 3.6 Beta 3 includes a major structural change that aims to improve the browser's stability. The Components Directory, which is where much of Firefox's code is stored, will be locked down, to exclude components from third-party developers.

Developers will still be able to extend Firefox using Add-ons and Plug-Ins, but the components directory is now off-limits.

Code installed in the components directory can't be managed like other add-ons, explains Mozilla's Johnathan Nightingale in an online post. It also offers no way to see version information, which is important for determining whether software is out of date.

An open Components Directory can lead to performance issues or crashing. Hence, the ban.

Beta 3 also adds a new HTML 5 feature, asynchronous script execution, which helps Web pages load faster.

The new beta comes with a slew of other features of interest to developers, such as device orientation detection and accelerometer support in Mac laptops.

Other features that debuted in earlier betas of Firefox 3.6 include a way to prevent incompatible software from making Firefox crash, support for browser themes called Personas, out-of-date plug-in alerts, support for the WOFF font format, a full-screen viewing option for videos embedded using the video tag, and a variety of performance improvements.

Mozilla has been celebrating Firefox's fifth anniversary and the occasion has coincided with another milestone: Earlier this month, Firefox crossed the 25% threshold for global market share, according to Net Applications.

And last month, for the first time -- at least by Net Applications' measure -- Firefox's global market share was larger than that of Internet Explorer 6.

The Firefox 3.6 Release Candidate is currently planned for November 26.

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