var ad_image=1;
  function show_flip_image(){
    document.getElementById('large_ad_window_img').src='PRM10/img/ads/large/ad'+ad_image+'_flip.jpg';
  }
  function show_image(){
    document.getElementById('large_ad_window_img').src='PRM10/img/ads/large/ad'+ad_image+'.jpg';
  }
  function load_ad_image(ref){
    ad_image=ref;
    show_image();
  }
  function ad_init(){
    document.getElementById('large_ad_window_img').onmouseover=show_flip_image;
    document.getElementById('large_ad_window_img').onmouseout=show_image;
  }