Mozilla Firefox specifications

New in version 21

• New: The Social API now supports multiple providers
• New: Enhanced three-state UI for Do Not Track (DNT)
• New: Firefox will suggest how to improve your application startup time if needed
• New: Preliminary implementation of Firefox Health Report
• Changed: Ability to restore removed thumbnails on New Tab Page
• Changed: CSS -moz-user-select:none selection changed to improve compatibility with -webkit-user-select:none (bug 816298)
• Changed: Graphics related performance improvements (bug 809821)
• Changed: Removed E4X support from Spidermonkey
• Developer: Implemented Remote Profiling
• Developer: Integrated add-on SDK loader and API libraries into Firefox
• HTML5: Added support for
  element
• HTML5: Implemented scoped stylesheets
• Fixed: Some function keys may not work when pressed (833719)
• Fixed: Browsing and Download history clearing needs unification to avoid confusion on clearing download history (847627)
• Fixed: 21.0: Security fixes can be found here