Mozilla has finally released the third beta of Firefox 3.1 after several delays brought on by show-stopping bugs in its new JavaScript engine TraceMonkey.

Testers can expect a speedier Gecko rendering engine for web pages from the latest beta, as well as more stable execution of JavaScript-based websites, said Mozilla.

Firefox 3.1 beta 3 comes with W3C Geolocation API, CSS 2.1 and 3 properties, SVG transforms and offline applications support.

It also boasts improved Private Browsing Mode for all your porn needs, better web worker thread support and new native JSON parsing support intended to protect the browser against possible code execution.

The group spun out the final beta of Firefox 3.1, codenamed Shiretoko, yesterday. Earlier this week Mozilla confirmed that a fourth beta would be released, followed by a release candidate version before the browser is finally shipped.

However, it will arrive under the name Firefox 3.5 to reflect the huge amount of changes in the development of the free browser, which is an incremental upgrade of Firefox 3.0, has undergone since its inception nine months ago.

Mozilla has been keen to emphasise that the version rename does not mean the browser’s shipping date will slip behind schedule even further. The open source organisation still expects to release Firefox 3.5 in the first half of this year.

In fact the firm’s Mike Beltzner has attempted to justify the oft-delayed release by saying the browser’s status has been upgraded and can no longer be considered as an inbetweeny version.

"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," he said on 5 March.

Firefox 3.1 had originally been expected to land in December last year. ®