<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
padding: 0 ;
margin: 0;
}
.box1,.box2,.box3{
border: 5px solid red;
height: 100px; }
.box2{
border-color: blue;
/*设置上右下左的外边距*/
/*margin: 10px 0 20px 200px;*/
/*上下为10,左右为200*/
margin: 10px 200px; }
.box4{
width: 900px;
height: 300px;
background-color: yellow;
/*设置水平居中*/
margin: 0 auto;
}
</style></head>
<body>
<div class="box1"></div>
<div class="box2"></div>
<div class="box3"></div>
<div class="box4"></div>
</body>
</html>
