<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>外部样式表css</title>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<details>
<summary>样式的三种方法</summary>
<ol>
<li>内联</li>
<li>内部</li>
<li>样式表</li>
</ol>
</details>
<p>这是一个例子</p>
</body>
</html>