bootstrap 预定义样式风格

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <!-- 处理低版本IE 4.0不考虑IE8 -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <!-- 移动端视口的设置 -->
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- 引入bootstrap.css -->
    <link rel="stylesheet" href="css/bootstrap.css">
    <style>
        #login{
            width:400px;
        }
    </style>
</head>
<body>
<div class="container">
    <br>
    <input type="button" value="默认样式">
    <input type="button" value="首选项" class="btn btn-primary">
    <input type="button" value="成功" class="btn btn-success">
    <input type="button" value="一般信息" class="btn btn-info">
    <input type="button" value="警告" class="btn btn-warning">
    <input type="button" value="危险" class="btn btn-danger">

    <br>
    <br>

    <p>默认段落</p>
    <p class="bg-primary">首选项</p>
    <p class="bg-success">成功</p>
    <p class="bg-info">一般信息</p>
    <p class="bg-warning">警告</p>
    <p class="bg-danger">危险</p>
    <br>
    <span>默认文字</span>
    <span class="text-primary">首选项</span>
    <span class="text-success">成功</span>
    <span class="text-info">一般信息</span>
    <span class="text-warning">警告</span>
    <span class="text-danger">危险</span>

    <br>
    <a href="#" class="btn btn-primary">连接1</a>
    <a href="#" class="bg-success">连接2</a>
    <a href="#" class="text-danger">连接3</a>
    <br><br>
    <div class="alert alert-warning">我是警告框</div>
    <div class="alert alert-danger">我是危险信息</div>
    <br><br>
    <div class="panel panel-primary">
        <div class="panel-heading">
            <h4>我是面板的标题</h4>
        </div>
        <div class="panel-body">
            我是面板的主体内容！
        </div>
    </div>

</div>
<div class="container">
    <br>
       <div id="login" class="panel panel-primary">
        <div class="panel-heading">
            Login
        </div>
        <div class="panel-body">
            <div class="form-group">
                <label>用户名:</label><input type="text" class="form-control">
                <div class="alert alert-warning">用户名不能为空！</div>
                <label>密码:</label><input type="password" class="form-control">
            </div>
            <a href="#" class="text-info">忘记密码?</a>
            <input type="button" value="登录" class="btn btn-primary pull-right">
        </div>
    </div>
</div>

</body>
<script>
    /*
        预定义样式风格
            primary (首选项)
            success (成功)
            info (一般信息)
            warning (警告)
            danger (危险)
            实例 ：登录框

     */
</script>