_header.html

<header>
    <nav class="navbar navbar-expand-sm navbar-dark bg-dark">
        <a class="navbar-brand" href="/">
            <img src="http://www.volgau.com/portals/_default/images/favicons/favicon-96x96.png" width="48" height="48" alt="ВолГАУ" class="rounded">
        </a>
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Меню">
            <span class="navbar-toggler-icon"></span>
        </button>
        <div class="collapse navbar-collapse" id="navbarSupportedContent">
            <ul class="navbar-nav">
                <li class="nav-item">
                    <a class="nav-link" href="/">Главная</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="directory.shtml"><strong>Каталог</strong></a>
                </li>
                <li class="nav-item dropdown">
                    <a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                        Справка
                    </a>
                    <div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
                        <a class="dropdown-item" href="help.shtml">Общие вопросы</a>
                        <a class="dropdown-item" href="help_editors.shtml">Редактору</a>
                    </div>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="http://www.volgau.com" target="_blank">Сайт ВолГАУ</a>
                </li>
            </ul>
        </div>
    </nav>
</header>