<script type="text/javascript">
function bookmarksite(title,url){
if (window.sidebar) // firefox
	window.sidebar.addPanel(title, url, "");
else if(window.opera && window.print){ // opera
	var elem = document.createElement('a');
	elem.setAttribute('href',url);
	elem.setAttribute('title',title);
	elem.setAttribute('rel','sidebar');
	elem.click();
} 
else if(document.all)// ie
	window.external.AddFavorite(url, title);
}
</script>

<a href="javascript:bookmarksite('Domain Name', 'http://www.domainname.com')">Bookmark Link</a>