For more information, including a link to a handful of microsummary sites you can test this out with, see this Mozilla Using Microsummaries wiki page. In initial testing, only some of example sites were working. Try the BBC link first.

It's all about the tabs

Mozilla has added several minor refinements to its tabbed browsing features, the best of which is a new Undo Close Tab function. Simply right-click the tab bar, and the last tab you closed during the current session will be resurrected when you choose the "Undo Close Tab" item from the pop-up menu. This functionality was previously available through a wide range of Firefox extensions, so formally including it in Firefox is a good move.

Right-click the tab bar and this pop-up menu will appear. If you've closed a tab in the current browser session, you can reopen it -- and the Web page loaded in it -- by choosing Undo Close Tab.

There's also a new Session Restore function that automatically offers to reopen all the tabs that were open in Firefox prior to some unexpected problem, such as a program or operating system crash or a power outage. Mozilla's implementation is particularly good in that when you restart Firefox after such an event, it offers the option to open the previously open tabs, or not. Many of the extensions that added this functionality for Firefox 1.x either always opened the previous tabs or required you to find a menu item somewhere to reopen them. This is the best way to handle it.