@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); 
/* only needed once */

#appmenu_bookmarksPopup menuseparator[builder="end"],
#appmenu_unsortedBookmarks,
#bookmarksMenuPopup menuseparator[builder="end"],
#menu_unsortedBookmarks,
#BMB_bookmarksPopup menuseparator[builder="end"],
#BMB_unsortedBookmarks {display:none!important;}