方块和盒子的单纯样式
<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>方块和盒子的单纯样式</title>
</head>
<style>
.top{
width:200px;
height:300px;
background: red;
color:#fff;
margin:20px auto 0;
font-size:50px;
line-height:300px;
text-align:center;
}
</style>
<body>
<div class="top">hello word!</div>
</body>
</html>