Mozilla 4 have released the first public beta of Firefox 4, and while it’s not exactly stable yet, the browser already includes some interesting changes that are well worth a closer look.

Take Flash, for instance – are you tired of applets crashing your browsing session? Mozilla are, too, and so beta 4 gains new crash prevention features to prevent this from happening. If Flash, QuickTime or Silverlight fail or lock up then they will no longer bring down the entire browser, and you can simply refresh the current page and try to view it again. Sounds good to us.

One obvious interface tweak sees the tabs relocated to the very top of the browser window, which Mozilla say this is giving them “top visual priority for more efficient and intuitive browsing”. Everyone else will say it’s just borrowing from Chrome, but either way, it does make for a cleaner, simpler interface.

And along the same lines, it’s good to see the menu bar replaced by a single Firefox button, top left of the screen. Clicking this gives you access to most of the options you need: New Window, Save Page As, Print, Find, History and so on. And again, it all helps to simplify the browser, cutting down the number of places where you must click to look for commands, and leaving the maximum amount of space available for the web page you’re viewing.

The Add-Ons Manager has been revamped, now taking up an entire tab of its own, and making it easier to uncover new extensions and manage the ones you have already.

And elsewhere there are privacy improvements, new support for HTML5 and CSS3, and several changes that could become very useful in the future. Indexed DB, for instance, will allow sites to store data locally, so apps like GDocs can work even when you’re not connected to the internet.

There’s plenty to explore, then, and performance seems good for a beta. If you’d like to give it a try, then download your copy here.