代码示例：（标识：bs_alerts_dismissible）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container mt-3">
<h2>警告框</h2>
<p>设置了 class="btn-close" 和 data-bs-dismiss="alert" 的按钮用于关闭警报框。</p>
<p>alert-dismissible 类将按钮向右侧对齐。</p>
<div class="alert alert-success alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>成功！</strong>此警报框表示成功或积极的动作。
</div>
<div class="alert alert-info alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>信息！</strong>此警报框表示中性的信息更改或操作。
</div>
<div class="alert alert-warning alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>警告！</strong>此警报框可能表示可能需要注意的警告。
</div>
<div class="alert alert-danger alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>危险！</strong>此警报框表示危险或潜在的负面操作。
</div>
<div class="alert alert-primary alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>基本！</strong>此警报框表示重要的动作。
</div>
<div class="alert alert-secondary alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>次要！</strong>此警报框表示不太重要的操作。
</div>
<div class="alert alert-dark alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>深色！</strong>深灰色警报。
</div>
<div class="alert alert-light alert-dismissible">
<button type="button" class="btn-close" data-bs-dismiss="alert"></button>
<strong>浅色！</strong>浅灰色警报。
</div>
</div>
</body>
</html>
