老师帮我看看我的代码正确吗？

来源：2-10 编程练习

慕妹8524794

2019-10-13 19:53:29

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
    /*完善下列代码*/
    .per{
     position:relative;
     width: 300px;
     height: 300px;
     background: red;
     margin-left:200px;
     margin-top: 200px;
   }   .son{
     position:absolute;
     width: 100px;
     height: 100px;
     background: blue;
     top:0;
     bottom:0;
     left:0;
     right:0;
     margin:auto auto;
   }
</style>
</head>
<body>
<div class="per">
    <div class="son"></div>
</div>
</body>
</html>