Here is your code snippet
Code
//change the two variables below
var bookmarkurl="http://www.yoursitehere.com";
var bookmarktitle="name of site here";
function addbookmark(){
if (document.all)
window.external.AddFavorite(bookmarkurl,bookmarktitle);
}
</script>
</head>
<body>
<a href="javascript:addbookmark()">Bookmark this site!</a>
</body>
</html>