function switchImage(imgName, imgSrc) 
{
  if (document.images)
  {
    if (imgSrc != "none")
    {
      document.images[imgName].src = imgSrc;
    }
  }
}
//Open a popup window and center it according to the user's screen and height & width.
function openWin(URL) {
	var w = 650
	var h = 600
	var winLeft = (screen.width - w) / 2;
	var winTop = (screen.height - h) / 2;
	windowName = "myWin";
	var windowFeatures = "width="+w+",height="+h+",status,scrollbars,resizable,"+"left="+winLeft+",top="+winTop 
	newWindow = window.open(URL, windowName, windowFeatures);
	newWindow.focus();
}