<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style type="text/css">
#div1{
/*内容区的宽度和高度*/
width: 300px;
height: 300px;
background-color: yellow;
/*设置边框*/
border-width: 50px;
border-color: red;
border-style: solid;
/*设置内边距*/
padding: 50px 100px 50px 100px;
}
#div2{
width: 300px;
height: 300px;
background-color: blue;
}
</style>
</head>
<body>
<div id="div1">
<div id="div2"></div>
</div>
</body>
</html>
整个盒子的尺寸 = 内容区的尺寸 + 2*内边距 + 2*边框