The work on Firefox 4 take longer than planned. The browser is not as originally planned later this month and not more this year also appear. This was announced by Mozilla's chief developer Mike Beltzner with Firefox. The new, provisional timetable , according to Firefox 4 is now released until early 2011.

Beltzner declared that there had been at work on the seventh beta version of delays. In particular, stability problems were encountered. Given the volume of the completion of Firefox 4 required work they had changed the schedule now. Because of the postponement of the final version of Mozilla wants three more beta releases published.

The seventh beta version will be the last, the original, now appears too late. According to Mozilla Firefox 4 Beta 7 is now published at the beginning of next month. By mid-December then to three more beta versions to push. Early 2011, then followed by one or more release candidates, and shortly after the final version. Mike Beltzner said that they would not deliver any unfinished software. This also means that there could be other delays.

Firefox 4 will include some major innovations, including a trimmed down user interface and the new and much faster JavaScript engine, "Hunter Monkey". Overall, Firefox 4 will be noticeably faster, both in the performance of web applications as well as the reaction of the browser on user input. In addition, Mozilla has changed the schedule for the mobile offshoot of Firefox. Fennec 2.0 for a third beta version was announced to appear at the end of November. The beta 2 will be released within the next few days. When the final version is published, is not yet known.