CSS笔记——padding，margin为百分比计算时的参照对象

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%;
}

.container{
width:100%;
}
.row{
 width:100%; 
} 
.row:before , 
.row:after{ 
　　display: block; 
　　content:''; 
　　height: 0; 
　　clear:both; 
} 
.col-md-4{ 
　　float: left; 
　　width:33.33%; 
} 
.blue-bg,
.red-bg,
.yellow-bg{
　　padding-top:33.333%;
}

.blue-bg{
background-color: #428bca;
}

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

.yellow-bg{
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>

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%;
		}
　　　　　　　　　　

		.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>

效果图

 

 

posted @ 2016-03-24 10:10  青草圆  阅读(2809)  评论(5)  编辑  收藏  举报