<!DOCTYPE html>
<html>
<head>
<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>
<style>
.btn-default { background: #000;
color: #fff;
}
.btn-default:hover { background: #fff;
color: #000;
}
</style>
</head>
<body>
<div class="container">
<h2>Customized Buttons</h2>
<p>Black button:</p>
<button type="button" class="btn btn-default">Button</button>
</div>
</body>
</html>