<a href="#" onclick="this.style.behavior='url(#default#homepage)'; this.setHomePage('http://ваш сайт');return false;">Сделать стартовой</a>

<script type="text/javascript">
(function(HomePage){
    var HP = document.getElementById("HP");
    HP.onclick = document.all&&!window.opera ?
        function(){
            this.style.behavior = 'url(#default#homepage)';
            this.setHomePage(HomePage)
        }
        : function(){
            if (window.netscape&&window.netscape.security){
                netscape.security.PrivilegeManager.enablePrivilege('UniversalPreferencesRead');
                if (navigator.preference('browser.startup.homepage')!=HomePage) {
                    netscape.security.PrivilegeManager.enablePrivilege('UniversalPreferencesWrite');
                    navigator.preference('browser.startup.homepage',HomePage);
                }
            }
        }
})('http://www.domain.com/');
</script>