Latest Release Features :
* Fixed a stability issue affecting Windows users.* Fixed an issue causing rendering errors with plugins affecting Mac OS X users.
* See the complete changelist from the previous beta.
As well as these features from previous Firefox 4 Betas:
* Firefox 4 Beta is available in 39 languages.
* Support for the new proposed Audio Data API
* Direct2D Hardware Acceleration is now on by default for Windows 7 users
* Firefox button has a new look for Windows Vista and Windows 7 users
* Support for HSTS security protocol allowing sites to insist that they only be loaded over SSL.
* Firefox Sync is now included by default.
* A new feature gives users a visual overview of all open tabs, allowing them to be sorted and grouped.
* An experimental API is included to provide more efficient Javascript animations.
* Firefox now supports the HTML5 video "buffered" property.
* Tabs are now on top by default on Windows and OSX - Linux will be changing when the theme has been modified to support the change.
* You can turn any tab into an "App Tab" by right-clicking on it and selecting "Make into App Tab" from the context menu.
* Web developers can animate content using CSS Transitions.
* Responsiveness and scrolling improvements from the new retained layers layout system.
* JavaScript speed improvements due to engine optimizations.
* Changes to how XPCOM components are registered in order to help startup time and process separation.
* You can search for and switch to already open tabs in the Smart Location Bar.
* New Addons Manager and extension management API (UI will be changed before final release).
* Significant API improvements are available for JS-ctypes, a foreign function interface for extensions.
* The stop and reload buttons have been merged into a single button on Windows, Mac and Linux.
* The Bookmarks Toolbar has been replaced with a Bookmarks Button by default (you can switch it back if you'd like).
* Crash protection for Windows, Linux, and Mac when there is a crash in the Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins.
* CSS Transitions are partially supported.
* Full WebGL support is included but disabled by default at this time.
* Core Animation rendering model for plugins on Mac OS X. Plugins which also support this rendering model can now draw faster and more efficiently.
* Native support for the HD HTML5 WebM video format.
* An experimental Direct2D rendering backend is available on Windows, turned off by default.
* Web developers can use Websockets for a low complexity, low latency, bidirectional communications API.
* Web developers can update the URL field without reloading the page using HTML History APIs.
* More responsive page rendering using lazy frame construction.
* Link history lookup is done asynchronously to provide better responsiveness during pageload.
* CSS :visited selectors have been changed to block websites from being able to check a user's browsing history.
* New HTML5 parser.
* Support for more HTML5 form controls.
* Web authors can now get touch events from Firefox users on Windows 7 machines.
* A new way of representing values in JavaScript that allows Firefox to execute heavy, numeric code (used for things like graphics and animations) more efficiently.
