var windowObjectReference = null; // global variable
var PreviousUrl; /* global variable which will store the
                    url currently in the secondary window */

function newWindow(strUrl, w, h)
{
  if(windowObjectReference == null || windowObjectReference.closed)
  {
   windowObjectReference = window.open(strUrl, "SingleSecondaryWindowName","width="+w+",height="+h+",resizable=no,scrollbars=yes,status=yes");
  }
  else if(PreviousUrl != strUrl)
  {
   windowObjectReference = window.open(strUrl, "SingleSecondaryWindowName","width="+w+",height="+h+",resizable=no,scrollbars=yes,status=yes");
    /* if the resource to load is different,
       then we load it in the already opened secondary window and then
       we bring such window back on top/in front of its parent window. */
   windowObjectReference.focus();
  }
  else
  {
    windowObjectReference.focus();
  };
  PreviousUrl = strUrl;
  /* explanation: we store the current url in order to compare url
     in the event of another call of this function. */
}