A new feature in Firefox 4 is the application or app tab. By “Pinning” a Tab as an App Tab, the tab is grouped to the far left, and only the Favicon shows. This is very useful when you have many tabs which you plan on keeping open all the time. To Pin/Unpin an app tab, right-click on the tab and select either Pin as App Tab or Unpin as App Tab. This can also double as a nice ‘privacy’ feature.
App Tabs are grouped to left. To restore an app tab to a normal tab, right-click on tab and deselect Pin as App Tab
