<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<nav class="navbar navbar-expand-sm bg-light navbar-light">
<ul class="navbar-nav">
<li class="nav-item active">
<a class="nav-link" href="#">Home</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">About</a></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Portfilo</a>
</li>
<li class="nav-item dropdown" >
<a class="nav-link " data-toggle="dropdown" href="#">Services</a>
<ul class="dropdown-menu">
<li><a href="#">Website Designing</a></li>
<li><a href="#">Website Development</a></li>
<li><a href="#">Content Writing</a></li>
<li><a href="#">PPC Services</a></li>
<li><a href="#">SMO</a></li>
<li><a href="#">SEO</a></li>
</ul>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Contact</a>
</li>
</ul>
</nav>
