Panorama and Sync features will be the major attractions of Firefox 4.
Mozilla has released Firefox 4 Beta 4, bringing new features along with enhanced existing features.The main features of Firefox 4 are Firefox Sync which synchronizes your data across multiple devices and Panorama new feature for grouping and organizing your tabs. Panorama was known as Tab Candy before.
Firefox 4 fixes flaws in the CSS Web standard that allowed your browser history to be exposed.
There are many improvements and additional features like the support to the WebM format so you can watch open HD quality video, WebSockets,HTML5 Support,Indexed DB ,Multi-touch Support (for Windows 7) etc..
The Firefox 4 Beta is currently available on Mac, Windows and Linux.