<!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://apps.bdimg.com/libs/bootstrap/3.3.0/css/bootstrap.min.css">
<script src="https://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>
<script src="https://apps.bdimg.com/libs/bootstrap/3.3.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Responsive Embed</h2>
<p>Create a responsive video and scale it nicely to the parent element with an 16:9 aspect ratio</p>
<div class="embed-responsive embed-responsive-16by9">
<iframe class="embed-responsive-item" src="https://www.youtube.com/embed/tgbNymZ7vqY"></iframe>
</div>
</div>
</body>
</html>