Mozilla firefox 21 stable is now available for download from Mozilla’s FTP site. It is currently not available on the firefox official homepage but expected to be available in May 14.
What’s new in this firefox 21?
Enhanced three-state UI for Do Not Track (DNT)
Firefox will suggest how to improve your application startup time if needed
Preliminary implementation of Firefox Health Report
Ability to Restore removed thumbnails on New tab Page
Add-ons History API removals in Places
CSS -moz-user-select:none selection changed to improve compatibility with -webkit-user-select:none
Graphics related performance improvements
Removed E4X support from SpiderMonkey
Implemented Remote Profiling
Integrated, Add-on SDK loader and API libraries into Firefox
Added support for < main > element
Implemented scoped stylesheets
Fixes:
Some function keys may not work when pressed
Browsing and Download history clearing needs unification to avoid confusion on clearing download history
and some security fixes