            border-bottom-left-radius: 0;
        }
        .form-signin input[type="password"] {
            margin-bottom: 10px;
            border-top-left-radius: 0;
            border-top-right-radius: 0;
        }
    </style>
</head>
<body class="text-center">
<div class="form-signin">
    <h1 class="h3 mb-3 font-weight-normal">在线留言板</h1>
    <br>
    <label for="username" class="sr-only">Username</label>
    <input type="text" id="username" name="username" class="form-control" placeholder=