boot2.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js"></script>
</head>
<body>
    <div class="container">
        <nav class="navbar bg-secondary">
            <ul class="navbar-nav">
                <li class="nav-item">
                    <a class="nav-link" href="Home.html">
                        Home
                    </a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="Contact_us.html">
                        Contact us
                    </a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="About_us.html">
                        About us
                    </a>
                </li>
            </ul>
        </nav>
    </div>
</body>
</html>