// Hide the grey overlay and the current gallery
  function hideOverlay() {
      // Make sure that we reset the current image
      curImage = null;
                  
      // and hide the overlay and gallery
      hide( id("overlay") );
      hide( id("gallery") );
  }
  
  // Show the grey overlay
  function showOverlay() {
      // Find the overlay
      var over = id("overlay");
                  
      // Make it as tall and wide as the entire page
      // (this helps with scrolling)
      over.style.height = pageHeight() + "px";
      over.style.width = pageWidth() + "px";
                  
      // And fade it in
      fadeIn( over, 50, 10 );
  }