function getCookie(cookie_name) {
        var allcookies = document.cookie;
        var cookie_pos = allcookies.indexOf(cookie_name);
        if (cookie_pos !== -1) {
          cookie_pos = cookie_pos + cookie_name.length + 1;
          var cookie_end = allcookies.indexOf(";", cookie_pos);
          if (cookie_end === -1) {
            cookie_end = allcookies.length;
          }
          var value = unescape(allcookies.substring(cookie_pos, cookie_end));
        }
        return value;
      }