引导警报类
通过创建包装器<div>并添加.alert类和四个上下文类之一来添加基本警报，例如.alert-success，.alert-info，.alert-warning，.alert-danger。
您可以尝试运行以下代码来创建警报类-
示例
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap Example</title>
<link href = "/bootstrap/css/bootstrap.min.css" rel = "stylesheet">
<script src = "/scripts/jquery.min.js"></script>
<script src = "/bootstrap/js/bootstrap.min.js"></script>
</head>
<body>
<div class = "alert alert-success">
This is Success!
</div>
<div class = "alert alert-info">
This is Info!
</div>
<div class = "alert alert-warning">
This is Warning!
</div>
<div class = "alert alert-danger">
This is Error!
</div>
</body>
</html>