Firefox automatically creates backups of your bookmarks and saves the last fiveten backups for safekeeping. This article describes how to manually back up your bookmarks, and replace them with a backup.
Click the Bookmarks button on the right side of the navigation toolbar (Windows XP: click the Bookmarks menu) and select Show All Bookmarks to open the Library window.On the menu bar, click Bookmarks and select Show All Bookmarks to open the Library window.At the top of the Firefox window, click the Bookmarks menu and select Show All Bookmarks to open the Library window.
In the Library window, click the Import and Backup button and then select Backup....
In the Bookmarks backup filename window that opens, choose a location to save the file, which is named bookmarks-"date".json by default. The desktop is usually a good spot, but any place that is easy to remember will work.
Save the bookmarks json file. The Bookmarks backup filename window will close and you can close the Library window.