Firefox 4 will have another exciting and useful feature: Users will be able to restore previous session at any point after start up. Firefox 4 will have an entry in the History menu to restore previous session, which can be used at any point to load previous session. Apple’s browser, Safari, has a similar feature where users can reopen all windows from the last session.
This feature will be available in the next Firefox 4 beta. Mozilla’s developer Paul O’Shannessy describes this as:
“This means that you no longer have to restore your whole session immediately at start up. This will be available through a menu item in the History menu. Restoring your previous session after you’ve browsed around will merge the sessions. You shouldn’t lose any new data by restoring your previous session. We did this primarily for 2 reasons:

1> We want faster start up times. By encouraging users to always resume their previous sessions, we give the impression that Firefox takes a long time to load up. But really, you’re loading 20, 50, 100+ tabs and that’s what is slow.
2> When you’re quitting, you there’s a good chance you have no idea if you’ll need your tabs next time.”
Option to restore your previous session at any point will boost up Firefox’s start up time, and help users to access their previous work. Firefox 4 is going to rock!
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just now you can do this also with a “about:sessionrestore” at anytime after opening.
but then it should open then normal “about:sessionrestore” form to select only some pages.
and it should have the possiblity only open the pages one by one. that means not a “restore previous session” button but also a “open the selected page button”
and it should also have the posiibility to move the links from here to the “Favourites” or to “scrapbook” page.