/**
 * Opens a window for displaying images.
 * Call this as the onclick event of an anchor as follows
 * <a href="image.jpg" target="rtrImage" onclick="return openImageWindow()">
 */
function openImageWindow() {
  var rtrImageWindow = window.open("", "rtrImage", "toolbar=0,width=640,height=480,resizable=0");
  rtrImageWindow.focus();
  return true;
}