[From Addons Home page]
Tab Mix Plus enhances Firefox’s tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager with crash recovery that can save and restore combination of opened tabs and windows.
To add this Addons into ur firefox browser, Tools –> Add-ons –> Get Add-ons, here search “Tab Mix plus” . Just install that and restart firefox browser. 🙂
It will be very useful for those who use multi-tabs, like me 😛 😀