<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style type="text/css">
.TU{height: 500px;background: red;}
.TU2{height: 200px;width:200px;background:green;);background-size:200px;}
.TU3{height: 50px;width: 50px;background: pink;}
.TU4{height: 50px;width: 50px;background: blue;}
</style>
</head>
<body>
<div class="TU">
<div class="TU2"><div>
</div>
<div class="TU3"></div>
<div class="TU4"></div>
</body>
</html>
标题
