Some links in your Favorites folder have an icon indicating the webpage. After a while those icons get replaced with the standard web icon again, due to the IE cache which gets cleaned according to your settings.
FavIconizer stores those icons in the favorites folder by creating a new subfolder and changing the attribute to 'hidden'. That way the folder for those icons doesn't show up in the favorites menu (even if you set "show hidden files/folders" in your settings).
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