padding内边距问题，设置上下左右都为10px了，为什么感觉左右起作用了，上下根本不是10px呢
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>填充</title>
<style type="text/css">
#box1{
width:100px;
height:100px;
padding:10px;
border:1px solid red;
margin:50px;
background-color:blue;
}
p{
background-color:red;
}
</style>
</head>
<body>
<div id="box1">
<p>盒子1</p></div>
</body>
</html>
