javascript 实现倒计时

<script type="text/javascript">
    var addTimer = function () {
    var list = [],
        interval;

        return function (id, time) {
            if (!interval)
                interval = setInterval(go, 1000);
            list.push({ ele: document.getElementById(id), time: time });
        }

        function go() {
            for (var i = 0; i < list.length; i++) {
                list[i].ele.innerHTML = getTimerString(list[i].time ? list[i].time -= 1 : 0);
                if (!list[i].time)
                list.splice(i--, 1);
             }
         }

        function getTimerString(time) {
            var not0 = !!time,
            d = Math.floor(time / 86400),
            h = Math.floor((time %= 86400) / 3600),
            m = Math.floor((time %= 3600) / 60),
            s = time % 60;
            if (not0)
                return "<font color='red'>" + d + "天" + h + "小时" + m + "分" + s + "秒</font>";
            else
                return "<font color='red'>奥运来了!</font>";
         }
     } ();

    addTimer("timer", 60);//60s倒计时
</script>

日期的传递可以通过一个hidden的表单来实现。例如：
<form name="testform" method="post">
    <span style="font-weight: bold;">还剩：</span><br>
    <input type="hidden" name="date_form" value="2008/07/01 00:00:00" />
    <input type="hidden" name="date_to" value="2008/08/08 00:00:00" />
    <span id="timer"></span>
</form>