Two weeks after the Mozilla executives’ promised move ahead on the much-delayed Beta 3 browser, Mozilla Corp Thursday announced the release of the third beta version of Firefox 3.1. However, the bugs in the JavaScript engine TraceMonkey, which were responsible for the long hold-up of Beta 3, are yet to be fixed.

Offering a compensation for the delay of Beta 3, the company executives have added a fourth beta to the schedule - the Beta 4 presently lined up for April 14 release. By then, Firefox 3.1 is expected to be renamed Firefox 3.5, to reflect the significant changes the browser has undergone since the initial, 10-month-old Firefox 3.0.

Going by Mozilla statements, Firefox 3.1 beta 3 comes with many improvements, like – an enhanced Private Browsing Mode; upgrading of its Gecko layout engine; stepped-up stability in TraceMonkey; new native JSON parsing support for protection of Firefox against code execution; as well as support for audio and video functions such as W3C Geolocation API, CSS 2.1 and 3 properties, JavaScript query selectors, SVG transforms and offline applications.

As has been a Mozilla precedent, the users have been cautioned that the beta is a groundwork version for testing reasons. Firefox Director, Mike Beltzner, clearly said in the company’s blog: “This is pre-release software: you may encounter compatibility problems with some Web sites and add-ons.”