It is possible to disable Firefox Australis UI and restore initial interface. Australis is new interface for Firefox that has currently landed in Nightly and available for testing. This will be available worldwide with Firefox 28 release in April 2014. Some already hated the new interface, some liked it. If you’ve enough reasons to revert/get back to old Firefox interface good news for those is that an add-on is available on AMO which does exactly that.
Reasons to hate Australis
- New curved tabs instead of squared ones
- Tabs always on top, the option to move them to bottom has been removed from about:config
- No add-on bar which displays add-on icons at the bottom of Firefox window
- Some more changes you can find while using Australis
Restore Firefox Classic Interface from Australis with Classic Theme Restorer add-on
Classic Theme Restorer extension available for Mac, Windows and Linux restores above said features- restores squared tabs, appmenu, add-ons bar, small icon view and some old buttons. After installing this extension and restart of browser, you can see old Firefox interface with squared tabs by default. Add-on bar and Tabs not on top and other changes to enable are available in add-on options.
To get back to Australis you need to disable or remove the add-on.