The Mozilla folks have made available the newest release of the Firefox web browser
. This release is for testers and developers only, and should not be used if you have no interest in trying out the latest build. The release notes
cover the recent changes. From the what's new document: "Fast back (and forward) - This very experimental feature allows much faster session history navigation. The feature is off by default but can be enabled for testing purposes by setting the browser.sessionhistory.max_viewers preference to a nonzero number."