标题标签可以设置一到六级:<h1>~<h6>,
①用标题标签可以发大并加粗字体
②一个标题独占一行
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<h1>一级标题</h1>
<h2>二级标题</h2>
<h3>三级标题</h3>
<h4>四级标题</h4>
<h5>五级标题</h5>
<h6>六级标签</h6>
</body>
</html>