function bookmark(book_url,book_text)
{
   if ((navigator.appName == "Microsoft Internet Explorer") && 
          (parseInt(navigator.appVersion) >= 4))
    {
        var url=book_url;
        var text=book_text;
        window.external.AddFavorite(url,text);
    }
    else
    {
        var hinweis = book_url; 
        if(navigator.appName == "Netscape")
        {
           hinweis += " mit der Tastenkombination STRG + D.";
        }
        hinweis += " zu den Favoriten hinzufügen";
        alert(hinweis);
    }
}