<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box{
width: 400px;
height: 400px;
background-color: red;
/* 解决margin-top塌陷问题 */
/* 1.设置border padding */
/* border: 1px solid green; */
/* padding: 1px; */
/* 2.设置overflow */
overflow: hidden;
}
/* 3.通过伪类
实际开发使用
*/
.clearfix:before{
content: "";
display: table;
}
.box1{
width: 100px;
height: 100px;
background-color: green;
margin-top: 50px;
}
</style>
</head>
<body>
<div class="box clearfix">
<div class="box1"></div>
</div>
</body>
</html>