.vmiddle {
  vertical-align: middle;
  display: table-cell;
  behavior:url(vmiddle.htc);
  }

<public:component lightweight="true">
<script language="javascript">
function CenterContentsVertical(){
  var h = this.clientHeight;
  var i = Math.round( ( h - this.scrollHeight ) / 2 );
  this.style.paddingTop = i + 'px';
  this.style.height = ( h - i ) + 'px';
  }
CenterContentsVertical(this);
</script>
</public:component>