栅格系统的基本使用

<div class="container">

        <fieldset>
            <form action="" method="POST">
                <legend>登录</legend>
                <div class="row">
                    <div class="col-md-offset-2">
                        <div class="form-group">
                            <label for="">用户名</label>
                            <input type="text" class="form-control" placeholder="请输入用户名">
                        </div>
                        <div class="form-group">
                            <label for="">密码</label>
                            <input type="password" class="form-control" placeholder="请输入密码">
                        </div>
                        <div class="cekcbox">
                            <label for=""><input type="checkbox">记住密码</label>
                        </div>
                        <button type="submit" style="color : white" class="btn btn-danger btn-block">登录</button>
                    </div>
                </div>
            </form>
        </fieldset>
    </div>