The first Beta development milestone of Firefox 4.0 is a great chance to get an early taste of the new graphical user interface that the open source browser now sports. Unveiled back in 2009, Mozilla’s plans for a radical UI redesign are coming to fruition, and Firefox 4.0 Beta 1 is a great example of this. Early adopters will get to test the new Beta Build with a completely overhauled GUI, now tailored to Windows Aero in Windows 7 and Windows Vista, featuring Tabs on Top and a new Menu Button per the Microsoft’s Ribbon/Fluent user interface design.

In the first video embedded at the bottom of this article, Alex Faaborg, Principal Firefox User Experience Designer at Mozilla, highlights some of the major elements of the Firefox 4.0 UI revamp. The second video has already been available for a while now, and is set up to explain why Mozilla decided to go for the repositioning of the Tabs above the Address Bar.

“The first Beta of Firefox 4 is here, and you can download it now. In this video we quickly review a few of the initial UI changes that have already landed, including: our Feedback UI and how to control user interface tests; Switch to Tab; Tabs on Top (more details in an earlier video); The Firefox Button (note that this is only the default UI for Windows 7 and Vista),” Faaborg added.

What must be underlined is that Firefox 4.0 is still in development. “This is a very early Beta, so a lot of features are not complete yet, and the interface is still rather unpolished,” Faaborg said. However, because Firefox 4.0 is in Beta, Mozilla is looking for as much feedback as possible. And in this regard, the feedback button is an excellent place to start when it comes down to sending your input to Mozilla. Of course, first you will have to actually download Firefox 4.0 Beta, and test it.

Firefox 4.0 Beta 1 is available for download here.