var image_popup=0;
function show_image_popup(url)
{
  if(image_popup)
  {
    if(!image_popup.closed) image_popup.close();
  }
  var left;
  var top;
  var width=750;
  var height=750;
  
  if (screen.availWidth) {
	width=screen.availWidth;
	left=0;
  	}
  else left=100;
  if (screen.availHeight) {
	height=screen.availHeight;
	top=0;
  	}
  else top=100;
  image_popup = open(url, 'image_popup', 'dependent=yes,toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,width='+width+',height='+height+',left='+left+',top='+top);
}