CSS3 背景属性 backgrund-clip
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.bordertest {
border: 30px solid red;
/* background: green; */
background-clip:content-box;
width:500px;
height:300px;
}
</style>
</head>
<body>
<div class="bordertest">
<hr>xxxxxxxxxxxxxx
<hr>xxxxxxxxxxxxxx
<hr>xxxxxxxxxxxxxx
<hr>xxxxxxxxxxxxxx
<hr>xxxxxxxxxxxxxx
<hr>xxxxxxxxxxxxxx
</div>
</body>
</html>
backgrund-clip有三个属性，限定背景出现的区域
默认为padding-clip