Aggiunto placeholder link nella navbar

            <a class="navbar-brand" href="#">InvMan</a>

        </div>

        <div id="navbar" class="navbar-collapse collapse">

            <form class="navbar-form navbar-right" role="form">

                <div class="form-group">

                    <input type="text" placeholder="Email" class="form-control">

            <ul class="nav navbar-nav">

                <li><a href="#">Scan</a></li>

                <li><a href="#">Esplora</a></li>

                <li><a href="#">Inserisci</a></li>

            </ul>

            <div class="navbar-nav navbar-right">

                <button href="#" class="btn navbar-btn">Log in</button>

            </div>

                <div class="form-group">

                    <input type="password" placeholder="Password" class="form-control">

                </div>

                <button type="submit" class="btn btn-success">Sign in</button>

            </form>

        </div><!--/.navbar-collapse -->

    </div>

</nav>