<!DOCTYPE HTML>
<html>
 <head><style>
   div.post {
     overflow: auto;
     height: 15px;
     border: 1px solid black;
   }
   div.filler {
     height: 16px;
     background: yellow;
   }
 </style></head>
 <body><div class="post"><div class="filler"></div></div></body>
</html>