function fixSize()
{
  var dw = document.body.clientWidth;
  var dh = document.body.clientHeight;

  var iframe = document.getElementsByTagName("IFRAME")[0];
  iframeHeight = iframe.clientHeight;  

  iframe.style.top = (dh - iframeHeight) / 2 +"px";


  // Om fixatie te geven van bv. 10 pixels:
  //
  //  iframe.style.top = (dh - (iframeHeight + 10)) / 2 +"px";


}