Mozilla has delayed the third beta of its Firefox 3.1 web browser, citing a "large number" of remaining bugs as the reason for the slip.

The setback won't affect the final release date for Firefox 3.1, a company executive said. "Right now we're not expecting this to delay our shipping target of late in the first quarter," said said Mike Beltzner, director of Firefox.

Firefox 3.1 Beta 3, which until this week was set to launch on January 26, will now release a week later, on February 2, according to a tentative schedule Mozilla posted on its website. "Due to the large number of outstanding P1 blockers, we are declaring a code slip," Mozilla said in notes published after its weekly status meeting.

The third beta is expected to be the last for Firefox 3.1, which at one time was projected by Mozilla to ship in final form as early as late 2008.

Mozilla Firefox 3.1 Beta 2 review

There are 15 bugs blocking Beta 3's release, Mozilla said elsewhere in the notes, referring to those unfixed flaws labeled 'P1', the company's designation for show-stopping problems. Among the unfixed bugs are ones related to Firefox 3.1's new privacy mode, dubbed 'Private Browsing', a feature that debuted in Beta 2 last December; and several connected with the new ability to drag tabs from the browsing window.

Mozilla added a third beta to the Firefox 3.1 process in late November, saying at the time that it needed the extra build to wrestle remaining bugs and allow more testing of new features, including Private Browsing and a faster JavaScript engine. At the time, Beltzner said that the additional beta would not have a "major impact" on the final delivery of Version 3.1.

But Beltzner also said then that Beta 3 would enter "code freeze" - a milestone after which changes are either forbidden outright or tightly restricted - in early January. Yesterday, however, Mozilla set January 25 as the beta's code freeze deadline.

Beltzner remained confident that Firefox 3.1 would still be ready for release this quarter. But he also offered a caveat, the same that most major software developers regularly tout. "Of course, Mozilla will continue to abide by our policy of only shipping software 'when it's ready,' he said, "meaning that we'll never publish a release that doesn't meet our strict criteria for quality, stability and performance."

Computerworld US