// the generic explain function
function explain(url) {
  if(url != null) {
    explainWin=open(url, "displayWindow",
		    "width=400,height=150,status=yes,toolbar=no,menubar=no,scrollbars=yes,alwaysRaised=yes");
  }
  else
    {
      alert("Target URL" +  url + "does not exist");
    }	
}