list-style-type属性允许你控制项目符号（也称为标记）的形状或样式。
<!DOCTYPE html>
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<html>
<head>
<title>TODO supply a title</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style type="text/css">
ol {
list-style-type: lower-roman;
}
</style>
</head>
<body>
<div>TODO write content</div>
<h1>对于一个无序列表</h1>
<h2>这个符号就可以应用</h2>
<p>它会自动帮你排列一个列表</p>
<ol>
<li>星期一</li>
<li>星期二</li>
<li>星期三</li>
<li>星期四</li>
<li>星期五</li>
</ol>
</body>
</html>