<html>
<head><style>
#colset { -moz-column-count: 1; }
#short  { height: 0px;          }
#tall   { height: 10000px;      }
</style></head>
<body>
 <div id="colset">
  <div id="short">
   <div id="tall"></div>
  </div>
 </div>
</body>
</html>