Hi, first try restarting Firefox - 3-bar menu > Exit Firefox in bottom right corner.

If that doesn't help, and in case a Refresh has occurred, please look on your Desktop for a file named Old Firefox Data - Refresh Firefox - reset add-ons and settings.

If the file isn't there, you can try this: Open bookmarks > Show All Bookmarks > Import and Backup > Restore, and see if you have a backup there.

If not, please see -

• Profiles - Where Firefox stores your bookmarks, passwords and other user data.

• Recover important data from an old profile.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you!

Note that if you see this happen then you can try to use "Organize -> Undo" in the Bookmarks Manager (Library) to see if you can undo this action.

You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• https://addons.mozilla.org/firefox/addon/places-maintenance/

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

If the Places Maintenance extension can't repair the places.sqlite database then remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database from the most recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox
• http://kb.mozillazine.org/Profile_folder_-_Firefox