i used "forget" set at two hours and it deleted all my history why?

Sorry about that. I don't think that this should happen Did you use the toolbar Forget button? * https://support.mozilla.org/kb/forget-button-quickly-delete-your-browsing-history Note that that will close all open tabs. You can check in Windows/File Explorer if there is a previous version of the places.sqlite file available. *Right-click: Properties > Previous Versions *http://windows.microsoft.com/en-US/windows7/Previous-versions-of-files-frequently-asked-questions You can use this button to go to the current Firefox profile folder: *Help > Troubleshooting Information > Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox Note that this will restore the bookmarks as well to the restore date, so if necessary then create a bookmarks backup to avoid more dataloss. *https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them *https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them