清除浮動帶來的影響有兩種方法：
1、利用clear屬性
2、利用after僞類
舉例說明：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<style>
#header{
height: 100px;
background-color: red;
}
#body{
/*height: 300px;*/
background-color: yellow;
}
#left{
height: 280px;
width: 15%;
background-color: #4cae4c;
float: left;
}
#center{
height: 280px;
width: 70%;
background-color: #3c763d;
float: left;
}
#right{
height: 280px;
width: 10%;
background-color: green;
float: left;
}
#bottom{
height: 10%;
background-color: #ffceb6;
/*清除浮動元素帶來的影響*/
clear: both;
}
/*清除浮動的方式二：利用僞類after*/
.clearfix:after{
content: "";
display: table;
clear: both;
}
#foot{
height: 100px;
background-color: #2e6da4;
}
</style>
<title>Float浮動</title>
</head>
<body>
<div>
<div id="header"></div>
<div id="body" class="clearfix">
<div id="left">左側div</div>
<div id="center">中間div</div>
<div id="right">右側div</div>
<!-- <div id="bottom">底部div</div>-->
</div>
<div id="foot"></div>
</div>
</body>
</html> 
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