Mozilla has released the fourth beta for it’s upcoming Firefox 3.5 browser. The long awaited “Private Browsing Mode” is finally available by default in this development release. Among other stuff are improvements to the TraceMonkey JavaScript engine and Gecko 1.9.1 layout engine, and support for HTML5 <video> and <audio> tags. Firefox 3.5 is fast approaching RC stage, but if you can’t wait for the final release, you can get this fairly stable beta from here.

Firefox 3 users have got news as well – Mozilla has released a small update (3.0.10) that fixes a security and a stability issue. To update, go to Help > Check for Updates in your Firefox window.