dissect the navbar bootstrap
<h1><a name="responsivebtn"></a>A responsive navigation bar with toggle button</h1>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent_resptb" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent_resptb">
<div class="navbar-nav">
<a class="nav-item nav-link active" href="#">Item1 Active</span></a>
<a class="nav-item nav-link" href="#">Item2</a>
<a class="nav-item nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Item3 Disabled</a>
</div>
</div>
</nav>