// Set the initial value of the pop-up window to Null

var newWin = null;


// Check to see if the pop-up window is open before doing anything
// If a previous pop-up window is open, close it

  function closeWin() {
    if (newWin && !newWin.closed && newWin.open) {
      newWin.close();
      newWin=null;
   }  
}  


// Center the pop-up window for 4.0+ browsers 
// Make sure to account for browser chrome when doing the subtraction.

  function openWin(url) {
    
    closeWin();
   
    if (document.getElementById || document.all || document.layers) {
      var screenWidth = screen.availWidth;
      var screenHeight = screen.availHeight;
      var xPos = (screenWidth - 260)/2;
      var yPos = (screenHeight - 230)/2;

      newWin = window.open(url,'popup','height=270,width=270,toolbar=no,menubar=no,status=no,location=no,scrollbars=no,left=' + xPos + ',top=' + yPos + ',screenX=' + xPos + ',screenY=' + yPos + '');
    }

    else {
        newWin = window.open(url,'popup','height=270,width=270,toolbar=no,menubar=no,status=no,location=no,scrollbars=no,left=' + xPos + ',top=' + yPos + ',screenX=' + xPos + ',screenY=' + yPos + '');
    }

    if (newWin.opener == null) newWin.opener = window;
        newWin.opener.name = "opener";
  
}