function encode(url)
{
  while(url.search(/&/) != -1)
  {
    url = url.replace(/&/,"?");
  }
  
  return(url);
}

//alert(document.referrer);
  
document.open();
document.write("<img src='index_img.php?gId=" + encode(document.referrer) + "' width='1' height='1' border='0'>");
document.close();