<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
.content{
height: 400px;
width: 400px;
margin: 0 auto;
border: 1px solid #666;
position: relative;
top: 200px;
}
.xx{
margin-top: 100px;
border: 1px dotted #666;
width: 400px;
}
.sx{
margin-top: 100px;
border: 1px solid #666;
width: 400px;
}
</style>
</head>
<body>
<div class="content">
<div class="xx"></div>
<div class="sx"></div>
</div>
</body>
</html>
效果
