In the meantime however, at least 2 other beta after beta 8 were provided, then at least one release candidate.

Now Mozilla has released the beta there are some 9 of Firefox 4.0 which fixes many bugs, 660 total. Certainly, it is less than Firefox 4.0 beta 8 that brought the correction of 1400 bugs, but it's still not bad.

In addition to these bug fixes, Firefox 4.0 beta 9 makes some changes, starting with the history that was reviewed as well as bookmarks, which improves performance at both the start as bookmarks.

In addition, the way Firefox handles JavaScript objects has changed. Several types of JavaScript objects exist and before they were all grouped together and the browser had to go pick this bunch of objects (heap) to find the one or ones he needed.

Now the SpiderMonkey JavaScript engine (sometimes called TraceMonkey or JägerMonkey) can compartmentalize things. In fact, all objects from the same origin are grouped as you can see from the illustrations.