Mozilla announced today that the next major version of Firefox is ready for testing. That would be Firefox 4 beta, and Mozilla says it includes faster start-up time and bookmarking, and that it caters to smoother complex animations. 

"Firefox 4 Beta is built for the way people use the Web today, offering more control over the browsing experience," the Mozilla team says. "It introduces a fresh new look and features like App Tabs and Panorama to make it easier and more efficient to navigate the Web. Firefox 4 Beta also includes performance enhancements to make everything faster from start-up time to page-load speed and the performance of Web applications and games. Firefox Sync is integrated into the browser with Firefox 4 Beta, giving you access to your Awesome Bar history, bookmarks, open tabs and passwords across computers and smartphones."

"Firefox 4 Beta also enables developers to create fun Web apps and websites," the team adds. "With full support for HTML5 features in Firefox 4 Beta, developers can create new ways for people to enjoy the Web. This includes WebM and HD video, 3D graphic rendering with WebGL, hardware acceleration and the Mozilla Audio API to help create visual experiences for sound. Director of Product Platform Management Chris Blizzard has a full overview of all developer tools in Firefox 4 Beta."

The beta can be downloaded here. It will be updated every few weeks so new features can be tested. If you’re having problems with your add-ons and the beta, there is an add-on compatibility reporter you can use to test them. 

The beta is available in over 50 languages, with more to come. While the beta is "feature complete", Mozilla says it will still look for ways to improve upon it for the Firefox 4 final release.