/* Improve the appearance of the navigation bar: */

   #nav-bar .toolbarbutton-icon
   { max-width: 24px !important;
     max-height: 24px !important;
     margin-top: 5px !important;
     margin-bottom: 5px !important;
     margin-left: 4.8px !important;
     margin-right: 4.8px !important; }