From MozillaZine Knowledge Base
To bookmark all open tabs:
- SeaMonkey: Open the Bookmarks menu and select "Bookmark this Group of Tabs". In the File Bookmark window, type in a name for the group of tabs, select a destination folder and click OK. A new bookmark for the group of tabs will be created .
- Firefox: Open the Add Bookmark dialog (Ctrl+D or "Bookmarks -> Bookmark This Page" or "Bookmark this page" in context menu). Check the "bookmark all tabs in a folder" checkbox. Change the name to be the name of the new bookmark folder you wish to create, and then select a parent folder. Finally, click OK. A folder with bookmarks to all open tabs will be created. You can later reopen the tabs you saved by middle-clicking the folder or selecting the "Open in Tabs" menu item.