! DOCTYPE html html head meta charset ="utf-8" title 菜鸟教程(runoob.com) / title link rel ="stylesheet" href ="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css" script src ="https://cdn.staticfile.org/jquery/2.1
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script> <script src="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script> </head> <body> <div class="container"> <h2>背景</h2> <p class="bg-danger">该段落使用了类 "bg-danger"。</p> <a class="bg-danger" href="/index.php">该链接使用了类 "bg-danger"。</a> </div> </body> </html>