function popUpWindow(url,w,h) {
   if (document.all) {
      var xMax = screen.width, yMax = screen.height;
   }
   else if (document.layers) {
      var xMax = window.outerWidth, yMax = window.outerHeight;
   }
   else {
      var xMax = 640, yMax = 480;
   }
   var x = w, y = h;
   var xOffset = (xMax - x)/2, yOffset = (yMax - y)/2;
   window.open(url,'4D', 'width='+x+',height='+y+',screenX='+xOffset+',screenY='+yOffset+',top='+yOffset+',left='+xOffset+'');
}