Mozilla delivers Firefox 3.5 Beta 4:

“Mozilla late on Monday released Firefox 3.5 Beta 4, the latest development preview of the company’s next browser, which has been delayed several times and now is tentatively slated to ship before the end of June.

The milestone features more work under the hood – particularly in stability and performance of the new TraceMonkey JavaScript engine – as well as tweaks to the private browsing mode and improvements to the underlying Gecko layout engine, said Mike Beltzner, director of Firefox.”

This is a beta release intended for developer testing, and there are still some unfixed issues from previous versions.

Firefox 3.5 Beta 4 can be downloaded for Mac OS X, Windows and Linux in 63 different languages from Mozilla’s site. Users already running Beta 3 will be notified of the available update in the next 48 hours.