The latest version of Firefox has the following changes:

Add-ons installed by third party programs are now disabled by default
Added a one-time add-on selection dialog to manage previously installed add-ons
Added Twitter to the search bar
Added a preference to load tabs on demand, improving start-up time when windows are restored
Improved tab animations when moving, reordering, or detaching tabs
Improved performance and memory handling when using and elements
Added CORS support for cross-domain textures in WebGL
Added support for HTML5 context menus
Added support for insertAdjacentHTML
Improved CSS hyphen support for many languages
Improved WebSocket support
Fixed several stability issues