浮动的目的：把多个盒子放在一行上清除浮动的目的：解决父盒子高度为0的问题清除浮动，也称闭合浮动注：本文不兼容IE6
未清除浮动实现情况：
清除后：
原代码：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>清除浮动</title> <style type="text/css"> .content{ width:960px; margin:100px auto; border: 1px solid #ccc; } .left{ width:400px; height: 200px; background-color: green; float: left; } .right{ width: 400px; height: 200px; background-color: red; float: right; } </style> </head> <body> <div class="content"> <div class="left"></div> <div class="right"></div> </div> </body> </html>
具体方法：1.额外标签法在含浮动标签后加兄弟盒子清除浮动例：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>清除浮动</title> <style type="text/css"> .content{ width:960px; margin:100px auto; border: 1px solid #ccc; } .left{ width:400px; height: 200px; background-color: green; float: left; } .right{ width: 400px; height: 200px; background-color: red; float: right; } .clearbox{ clear:both; } </style> </head> <body> <div class="content"> <div class="left"></div> <div class="right"></div> <div class="clearbox"></div> </div> </body> </html>缺点：添加了许多空div
2.给父盒子overflow:hidden 触发bfc模式（该名词不懂请谷歌/百度，初学者可暂时略过)，直接清除浮动
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>清除浮动</title> <style type="text/css"> .content{ width:960px; margin:100px auto; border: 1px solid #ccc; overflow: hidden; } .left{ width:400px; height: 200px; background-color: green; float: left; } .right{ width: 400px; height: 200px; background-color: red; float: right; } .clearbox{ clear:both; } </style> </head> <body> <div class="content"> <div class="left"></div> <div class="right"></div> </div> </body> </html>缺点：不可与position属性配合使用
3.伪元素法给父元素定义伪类:after(此处使用的是公共类clearfix）
.clearfix:after{ content:"";/*内容为空*/ visibility:hidden;/*将元素隐藏，但是在网页中该占的位置还是占着*/ display:block;/*变成块级元素*/ height:0; clear:both;/*清除浮动*/ }
具体代码：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>清除浮动</title> <style type="text/css"> .clearfix:after{ content:"";/*内容为空*/ visibility:hidden;/*将元素隐藏，但是在网页中该占的位置还是占着*/ display:block;/*变成块级元素*/ height:0; clear:both;/*清除浮动*/ } .content{ width:960px; margin:100px auto; border: 1px solid #ccc; } .left{ width:400px; height: 200px; background-color: green; float: left; } .right{ width: 400px; height: 200px; background-color: red; float: right; } .clearbox{ clear:both; } </style> </head> <body> <div class="content clearfix"> <div class="left"></div> <div class="right"></div> </div> </body> </html>
缺点：IE8以上和非IE浏览器才支持
4.双伪元素法给父类加上伪类:before和:after
.clearfix:before,.clearfix:after{ content:""; display:table; } .clearfix:after{ clear:both; }具体代码：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>清除浮动</title> <style type="text/css"> .clearfix:before,.clearfix:after{ content:""; display:table; } .clearfix:after{ clear:both; } .content{ width:960px; margin:100px auto; border: 1px solid #ccc; } .left{ width:400px; height: 200px; background-color: green; float: left; } .right{ width: 400px; height: 200px; background-color: red; float: right; } .clearbox{ clear:both; } </style> </head> <body> <div class="content clearfix"> <div class="left"></div> <div class="right"></div> </div> </body> </html>附：对于上述4种方法，优先推荐方法3和4，当然1和2也可，可根据具体情况使用。还有几种乱七八糟的清除浮动方法，但是缺点多，故不提起，了解可参考：http://www.jb51.net/css/173023.html
转载于:https://www.cnblogs.com/lyxuefeng/p/9070566.html
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