The Most Visited bookmarks folder is placed in the Firefox bookmark’s toolbar displaying the most visited items that can be found in the Firefox history. The Recently Bookmarked folder contains all the recent bookmarks that have been added to Firefox while the Recent Tags folder does the same for tags that the user added.

All but the Unsorted Bookmarks folder can be deleted easily by right-clicking the entry and selecting delete from the menu. Once they are deleted there is no obvious way to get the folders back.

There is however an easy way to reset the special folders so that they appear again in Firefox 3 after a restart. To do that the user needs to enter about:config in the Firefox address bar and filter for the name browser.places.smartBookmarksVersion in there.

Only that entry should appear now. A right-click on that entry and the selection of Reset will reset the folders and activate them again after a restart of the Firefox browser.