One of the best new features in Firefox 4 is the tab groups feature (panorama), made for users who use lots of tabs and need an organized browsing experience.
To get to the Firefox Panorama feature click the arrow towards the end of your tabs and select ‘tab groups’ (see image below) or use the shortcut Ctrl + Shift + E.
Once you’ve clicked on the Panorama button drag your tabs into an empty space to create a new group. To search for tabs start typing in the tab groups panel or click on the search icon. Groups can be renamed using the pencil icon and deleting unwanted tabs is simply the ‘x’ button.
Once you have created your tab groups they are accessible again in the tabs bar. More information is available in this Firefox YouTube video: