Mozilla Firefox 4.0 and later versions come with a new feature called "Tab Groups" (aka Panorama) which can be accessed by clicking on small rectangle present at the right-side end of Tab bar or by using "View -> Tab Groups" menu or by pressing "Ctrl+E" keys together.
When you invoke this feature, a little smooth animation is shown. The same animation is shown when you close the Tab Groups window.
In this tutorial, we'll tell you how to disable this animation:
1. Open Firefox and type about:config in the addressbar and press Enter. It'll confirm, click on I'll be careful, I promise! button.
2. Now type animate in the Filter box and look for following boolean key:
3. The entry "browser.panorama.animate_zoom" would be set to true. Double-click on it or right-click on it and select "Toggle". It'll set its value to false.
4. Now whenever you open Tabs Group, you'll not see any animation and it'll load a bit faster.