JS錯誤頁指定時間跳轉

錯誤頁
   <script language="javascript" type="text/javascript">
        var i = 5;
        var intervalid;
        intervalid = setInterval("fun()", 1000);
        function fun() {
            if (i == 0) {
                window.location.href = "default.aspx";
                clearInterval(intervalid);
            }
            document.getElementById("mes").innerHTML = i;
            i--;
        }
    </script>
將在 <span id="mes">5</span> 秒鐘后返回首頁！