A new Beta of Firefox 3.1 was released yesterday.

Firefox 3.1 Beta 3 is the fifth development milestone and third beta release of Firefox 3.1, the next version of the Firefox web browser. While this release is considered to be stable, it is intended for developers and members of our testing community to use for early evaluation and feedback.

Read the full Release Notes here: http://www.mozilla.com/en-US/firefox/3.1b3/releasenotes/

Downloads (64 different languages) here: http://www.mozilla.com/en-US/firefox/all-beta.html

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Yeah, I tried the trunk build yesterday.

Yeah, I tried the trunk build yesterday.

The Trunk is the long-range development track, those builds contain improvements (hopefully) that won't be included in Firefox 3.1 - but they've now decided to release 3.1 as 3.5, since it contains so much new stuff (or because it's taking sooo long ). See suggested version number change for 3.1 • mozillaZine Forums .

There's going to be a beta 4, too - called 3.5 beta 4.

Trunk builds often perform better, but are more likely to be unstable (they're labeled Minefield instead of Firefox). Recent Trunk builds have been very good, though; I run them all the time. Branch builds are the ones leading to the next release - the current Branch is labeled Shiretoko, which is the code name for the 3.1/3.5 release. For more (somewhat dated) info, see Trunk & Branch Builds FAQ - MozillaZine Forums.