1. 使用额外标签法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.outer{
border: 1px solid black;
210px;
}
.inner{
50px;
height: 50px;
background-color: #005FC3;
margin:0 10px;
float: left;
}
.footer{
background-color: #ff4400;
212px;
height: 100px;
}
.clearfix{
clear: both;
}
</style>
</head>
<body>
<div class="outer">
<div class="inner"></div>
<div class="inner"></div>
<div class="inner"></div>
<div class="clearfix"></div>
</div>
<div class="footer"></div>
</body>
</html>

这是早期普遍使用的方法,但是对于有代码洁癖的人来说,解决的不够完美
2. 使用 :after 为元素
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.outer{
border: 1px solid black;
210px;
}
.inner{
50px;
height: 50px;
background-color: #005FC3;
margin:0 10px;
float: left;
}
.footer{
background-color: #ff4400;
212px;
height: 100px;
}
.clearfix:after{ /*最简方式*/
content: '';
display: block;
clear: both;
}
/* 新浪使用方式
.clearfix:after{
content: '';
display: block;
clear: both;
height: 0;
visibility: hidden;
}
*/
.clearfix{ /*兼容 IE*/
zoom: 1;
}
</style>
</head>
<body>
<div class="outer clearfix">
<div class="inner"></div>
<div class="inner"></div>
<div class="inner"></div>
</div>
<div class="footer"></div>
</body>
</html>

3. 给父元素定高
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.outer {
border: 1px solid black;
210px;
height: 50px;
}
.inner {
50px;
height: 50px;
background-color: #ff4400;
margin: 0 10px;
float: left;
}
.footer {
background-color: #005FC3;
212px;
height: 100px;
}
</style>
</head>
<body>
<div class="outer">
<div class="inner"></div>
<div class="inner"></div>
<div class="inner"></div>
</div>
<div class="footer"></div>
</body>
</html>

4. 利用 overflow:hidden 属性
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
.outer{
border: 1px solid black;
210px;
overflow: hidden;
zoom: 1;/*兼容 IE*/
}
.inner{
50px;
height: 50px;
background-color: #005FC3;
margin:0 10px;
float: left;
}
.footer{
background-color: #ff4400;
212px;
height: 100px;
}
</style>
</head>
<body>
<div class="outer">
<div class="inner"></div>
<div class="inner"></div>
<div class="inner"></div>
</div>
<div class="footer"></div>
</body>
</html>
