<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript" src="shangjia/jquery-1.8.0.min.js"></script>
<style>
	h1 {
		font-family:"微软雅黑";
		font-size:40px;
		margin:20px 0;
		border-bottom:solid 1px #ccc;
		padding-bottom:20px;
		letter-spacing:2px;
	}
	.time-item strong {
		background:#C71C60;
		color:#fff;
		line-height:49px;
		font-size:36px;
		font-family:Arial;
		padding:0 10px;
		margin-right:10px;
		border-radius:5px;
		box-shadow:1px 1px 3px rgba(0,0,0,0.2);
	}
	#day_show {
		float:left;
		line-height:49px;
		color:#c71c60;
		font-size:32px;
		margin:0 10px;
		font-family:Arial,Helvetica,sans-serif;
	}
	.item-title .unit {
		background:none;
		line-height:49px;
		font-size:24px;
		padding:0 10px;
		float:left;
	}
</style>
<script type="text/javascript">
	
	var date1=new Date();  //开始时间
	var temper="2015-11-12 14:28:25";
	var date2 = new Date(temper.replace(/-/,"/"));   //结束时间
	var date3=date2.getTime()-date1.getTime();  //时间差的毫秒数
	var intDiff = parseInt(date3/1000);//倒计时总秒数量
	function timer(intDiff){
		window.setInterval(function(){
		var day=0,
			hour=0,
			minute=0,
			second=0;//时间默认值       
		if(intDiff > 0){
			day = Math.floor(intDiff / (60 * 60 * 24));
			hour = Math.floor(intDiff / (60 * 60)) - (day * 24);
			minute = Math.floor(intDiff / 60) - (day * 24 * 60) - (hour * 60);
			second = Math.floor(intDiff) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);
		}
		if (minute <= 9) minute = ‘0‘ + minute;
		if (second <= 9) second = ‘0‘ + second;
		$(‘#day_show‘).html(day+"天");
		$(‘#hour_show‘).html(‘<s id="h"></s>‘+hour+‘时‘);
		$(‘#minute_show‘).html(‘<s></s>‘+minute+‘分‘);
		$(‘#second_show‘).html(‘<s></s>‘+second+‘秒‘);
		intDiff--;
		}, 1000);
	} 
	$(function(){
		timer(intDiff);
	});
</script>
</head>
<body>
	<h1>网页上的倒计时</h1>
    <div class="time-item">
        <span id="day_show">0天</span>
        <strong id="hour_show">0时</strong>
        <strong id="minute_show">0分</strong>
        <strong id="second_show">0秒</strong>
    </div>
</body>
</html>
原文:http://www.cnblogs.com/lanliying/p/4953762.html