function toggleLayer( whichLayer, htmlfile, targetframe )
{
  var elem, elframe, vis;
  //alert ("<iframe class='txt_InfoScreen' width='500px' height='570px' src='" + htmlfile + "'></iframe>");
if( document.getElementById ) // this is the way the standards work
   {elem = document.getElementById( whichLayer );
    elframe = document.getElementById( targetframe );}
  else if( document.all ) // this is the way old msie versions work
    {elem = document.all[whichLayer];
	 elframe = document.all[targetframe];}
  else if( document.layers ) // this is the way nn4 works
    {elem = document.layers[whichLayer];
	 elframe = document.layers[targetframe];}
  vis = elem.style;
  // if the style.display value is blank we try to figure it out here
  if(vis.display==''&&elem.offsetWidth!=undefined&&elem.offsetHeight!=undefined)
    vis.display = (elem.offsetWidth!=0&&elem.offsetHeight!=0)?'block':'none';
  vis.display = (vis.display==''||vis.display=='block')?'none':'block';
  elframe.innerHTML="<iframe class='txt_InfoScreen' width='500px' height='570px' src='" + htmlfile + "'></iframe>";
}