A new HTML5 parser and full support for web video, audio, drag & drop, and file handling means Firefox 4 is ready to run the best web apps of both today and tomorrow.
Stylin’ Pages with CSS3
With support for new CSS3 features, web designers can make their pages both look prettier and display faster.
Developers will be able to store application data locally, making cloud applications like Gmail or GDocs work more quickly and reliably, even when not connected to a network.
Firefox provides uninterrupted browsing for Windows, Linux, and now Mac when there is a crash in the Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins. If one of these commonly-used plugins crashes or freezes, it won’t affect the rest of Firefox. Instead, you can simply reload the page to restart the plugin and try again.
You can download firefox 4.0 Beta from Mozilla’s website