#menu_vert { width: 100%; background: #CCFFFF; } 
#menu_vert ul { list-style: none; margin: 0; padding: 0;} 
#menu_vert a, #menu_vert h2 {
  font: bold 11px/16px arial, helvetica, sans-serif;
  display: block; border-width: 1px; border-style: solid;
  border-color: #ccc #888 #555 #bbb;
  margin: 0; padding: 2px 3px; }
#menu_vert h2 { color: #000000; background: #CCFFFF;} 
#menu_vert a { color: #000; background: #CCFFFF; text-decoration: none; } 
#menu_vert a:hover { color: #a00; background: #fff; } 
#menu_vert li { position: relative; }
#menu_vert ul ul ul {position: absolute; top: 0; left: 100%; width: 200%; }

div#menu_vert ul ul ul,
div#menu_vert ul ul li:hover ul ul {display: none;} 
div#menu_vert ul ul li:hover ul,
div#menu_vert ul ul ul li:hover ul {display: block;}