上：top
下：bottom
左：left
右：right
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>css</title>
<style type="text/css">
div{
width:300px;height:100px;line-height:100px;text-align:center;background:#F7F7F7;
border-top:blue double 8px;
border-bottom:green double 8px;
border-left:red double 8px;
border-right:purple double 8px;
}
</style>
</head>
<body>
<div>我要好好学习</div>
</body>
</html>
返回值：