I have a number of links on my Bookmarks Toolbar for quick access. Each of them used to have an icon associated with it, but now one icon is missing. The link still works OK, so it's just a matter of not being able to spot it quickly with the icon. How can I tell FF what icon to use for a link? I can't do it on the toolbar or in the properties function for any link. I thought I used to be able to change it at will.