源代码 ：
点击运行
<!DOCTYPE html> <html> <head> <title>Bootstrap 实例</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script> <script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script> </head> <body> <div class="container"> <h1>更小文本标题</h1> <p>small 元素用于字号更小的颜色更浅的文本:</p> <h1>h1 标题 <small>副标题</small></h1> <h2>h2 标题 <small>副标题</small></h2> <h3>h3 标题 <small>副标题</small></h3> <h4>h4 标题 <small>副标题</small></h4> <h5>h5 标题 <small>副标题</small></h5> <h6>h6 标题 <small>副标题</small></h6> </div> </body> </html>
运行结果