感谢道友文章：http://www.zztuku.com/JS/Times/20130104_5550.html

贴代码：

body,div{margin:0;padding:0;} body{color:#fff;font:16px/1.5;} #down_wwwzzjsnet{width:300px;text-align:center;background:#1a1a1a;margin:10px auto;padding:20px 0;} input{border:0;width:283px;height:50px;cursor:pointer;margin-top:20px;background:url(http://www.zzjs.net/img/20120410wwwzzjsnet_1.png) no-repeat;} input.cancel{background-position:0 -50px;} span{color:#000;width:80px;line-height:2;background:#fbfbfb;border:2px solid #b4b4b4;margin:0 10px;padding:0 10px;} window.onload = function () { var oCountDown = document.getElementById("down_wwwzzjsnet"); var aInput = oCountDown.getElementsByTagName("input")[0]; var timer = null; aInput.onclick = function () { this.className == "" ? (timer = setInterval(updateTime, 1000), updateTime()) : (clearInterval(timer)); this.className = this.className == '' ? "cancel" : ''; }; function format(a) { return a.toString().replace(/^(\d)$/,'0$1') } function updateTime () { var aSpan = oCountDown.getElementsByTagName("span"); var oRemain = aSpan[0].innerHTML.replace(/^0/,'') * 60 + parseInt(aSpan[1].innerHTML.replace(/^0/,'')); if(oRemain