function yourLoadHandler()
{
  var iframe = document.getElementById('imenu'); 
  var browsername = navigator.appName;
  if (browsername.indexOf("Netscape")!=-1) 
  {
    var innerDoc = (iframe.contentDocument) ? iframe.contentDocument : iframe.contentWindow.document;
    iframe.height = innerDoc.body.offsetHeight + 32; //FF
  }
  else
  {
    iframe.height = iframe.document.body.scrollHeight; // IE
  }
}

if (typeof window.addEventListener != 'undefined') 
{
  window.addEventListener('load', function(evt) {yourLoadHandler();}, false);
}
else if (typeof window.attachEvent != 'undefined') 
{
  window.attachEvent('onload', function() {yourLoadHandler();})
}