<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>制作我的第一个网页</title>
<style type="text/css">
.triangle{width:100px;height:100px;
border-style:100px solid;
border-color:red green yellow blue;}
</style>
</head>
<body>
<div class="triangle">Hello World</div>
</body>
</html>
border:100px solid;不是border-style