This extension adds that feature to Firefox.
https://addons.mozilla.org/EN-US/firefox/addon/show-parent-folder/

just a little addition to what Ed wrote.

After installing the extension you will need to display the "Parent folder" column via the View columns menu in the Library list, or by right clicking on any column header in the library list and picking the columns you want to show. Also in the Add-ons options there are are two additional options available and suggest that you checkmark the "Show folder hierarchy".

I see that that is now all covered in the description and pictures on the extensions add-on's page -- greatly improved documentation.

You might want to check out this page as well for additional help with working with bookmarks. http://kb.mozillazine.org/Sorting_and_rearranging_bookmarks_-_Firefox

Thanks a lot, Just what I was looking for, shame it takes an add on to have this. This should be built in the browser. Again Thanks. Worked Great.