// Reposition the gallery to be at the center of the page
  // even when the page has been scrolled
  function adjust(){
      // Locate the gallery
      var obj = id("gallery");
                  
      // Make sure that the gallery exists
      if ( !obj ) return;
                  
      // Find its current height and width
      var w = getWidth( obj );
      var h = getHeight( obj );
                  
      // Position the box, vertically, in the middle of the window
      var t = scrollY() + ( windowHeight() / 2 ) - ( h / 2 );
                  
      // But no heigher than the top of the page
      if ( t < 0 ) t = 0;
                  
      // Position the box, horizontally, in the middle of the window
      var l = scrollX() + ( windowWidth() / 2 ) - ( w / 2 );
                  
      // But no less than the left of the page
      if ( l < 0 ) l = 0;
                  
      // Set the adjusted position of the element
      setY( obj, t );
      setX( obj, l );
  };
  
  // Readjust the position of the gallery every time
  // the user scrolls the page or resizes the browser
  window.onresize = document.onscroll = adjust;