Firefox 29 ships with an interface redesign called Australis, a new customization mode that goes along with it, and a redesigned Firefox Sync synchronization feature that is incompatible with the old.
Mozilla will make available Firefox 29 to all users of the stable version of the web browser over the course of the next 24 hour period.
Existing installations will be updated to Firefox 29 in that period if they have enabled automatic updates in the browser. The same is true for Beta, Aurora and Nightly versions of the browser which will receive an update to the next version as well, in this case version 30, 31 and 32 respectively.
The update to already available on the official Mozilla FTP repository and third-party sites. While you may head over to one of those download locations right now, it is usually better to wait until the release is officially announced as last minute changes may replace the current build with a different one.
You can check which version you are running by tapping on Alt, and selecting Help > About Firefox from the options menu. Alternatively, load about:support in the browser’s address bar right away.
For more details go to ghacks.net’s article located here.