<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet"
href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<button type="button" class="btn btn-info" data-toggle="collapse"
data-target="#demo">click to collapse</button>
<div id="demo" class="collapse">
Bootstrap is a free and open-source front-end web framework for designing <br />
websites and web applications. <br />
It contains HTML and CSS.
</div>
</div>
</body>
</html>
