The current stable Firefox version is 4 and version 5 Beta channel is there for testing new features which are a bit stable and needs user feedback, Mozilla has now initiated a brand new "Aurora" branch which should be considered the "ALPHA" stage featuring the newest innovations before they go to beta channel and will finally get released as "Firefox 6".

Currently "Firefox Aurora" provides users and Web developers more control over their browsing and development environments while improving overall performance, the new experimental "Data Management Window" feature allows users to define and control access of private data to specific websites, a new and revamped Add-ons Manager and plugin-checker now allows quick verification of compatibility.