<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
body{
/*取消浏览器外间距*/
margin: 0;
}
.c1{
60%;
height: 200px;
border: 1px solid green;
/*auto水平居中*/
margin: 100px auto;
}
.c2{
80%;
height: 45px;
border: 1px solid red;
margin: 0 auto;
}
</style>
</head>
<body>
<div class="c1">
<div class="c2"></div>
</div>
</body>
</html>