CSS笔记padding，margin为百分比计算时的参照对象

CSS笔记padding，margin为百分比计算时的参照对象 - 青草圆

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Release： 2016-05-21 08:42:33

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div的padding为百分比的两种情况

padding-top,padding-bottom,margin-top,margin-bottom是百分比时是按照当前元素的父级元素的宽度来计算的

1. 当子div的宽度是百分比时

html代码

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<meta chaset="utf-8">
<title>无标题</title>
<style type="text/css">
html,body{
margin:0;
padding:0;
height:100%;
}<br /><br />

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.container{
width:100%;
}

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.row{<br /> width:100%; <br />} <br />.row:before , <br />.row:after{ <br />　　display: block; <br />　　content:''; <br />　　height: 0; <br />　　clear:both; <br />} <br />.col-md-4{ <br />　　float: left; <br />　　width:33.33%; <br />} <br />.blue-bg,<br />.red-bg,<br />.yellow-bg{<br />　　padding-top:33.333%;<br />}<br />
.blue-bg{
background-color: #428bca;
}

.red-bg{
background-color: red;
}

.yellow-bg{
background-color: yellow;
}

<br />
</style>
</head>
<body>
<div class="container">
<div class="row">
<div class="col-md-4 blue-bg"></div>
<div class="col-md-4 red-bg"></div>
<div class="col-md-4 yellow-bg"></div>
</div>
</div>
</body>
</html>

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效果图

2. 当子div的宽度是具体像素时

html

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<meta name="viewport" content="width=device-width , initial-scale=1">
<meta chaset="utf-8">
	<title>无标题</title>
	<style type="text/css">
		html,body{
			margin:0;
			padding:0;
			height:100%;
		}<br />　　　　　　　　　　

		.row{
			width:100%;
		}

		.row:before , .row:after{
			display: block;
			content:'';
			height: 0;
			clear:both;
		}

		.col-md-4{
			float: left;
			width:100px;
		}

		.blue-bg{
			padding-top: 100%;
			background-color: #428bca;
		}

		.red-bg{
			padding-top: 100%;
			background-color: red;
		}

		.yellow-bg{
			padding-top: 100%;
			background-color: yellow;
		}

		
	</style>
</head>
<body>
	<div class="container">
		<div class="row">
			<div class="col-md-4 blue-bg"></div>
			<div class="col-md-4 red-bg"></div>
			<div class="col-md-4 yellow-bg"></div>
		</div>
	</div>
</body>
</html>

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效果图