js5秒倒计时

    <script language="javascript" type="text/javascript">        var i = 5;       intervalid= setInterval("fun()", 1000);        function fun() {            if (i == 0) {                window.location.href = "default.aspx";                clearInterval(intervalid);        }            document.getElementById("mes").innerHTML = i;            i--;        }    </script>