This is already a built in feature in Firefox, set start page to Show Tabs From Last Time.
Posted by: Anonymous
on November 12, 2007 04:55 PM
If you are using Firefox in Ubuntu (and maybe other Linux?), the preferences are under the Edit menu rather than the Tools menu.
But basically, the option where you set the starting page (usually home page or blank) has the session saving entry "Show my windows and tabs from last time".