<script type="text/javascript">
  function GetUrl(s) {
    var m = new Image();   
    m.src = s;   
    return m.src;   
  }; 
</script>

<A class="top" onclick="this.style.behavior='url(#default#homepage)';this.setHomePage(GetUrl('Index.aspx'));" ref="#">
  设为首页
</A>