Internet has evolved a lot since first website was made. Hence, the W3C has laid down standards to make html content accesscible and user-friendly to all users. Layout options and the standards implementented to make content acessible by assistive technologies.
<header role="banner">
<nav class="navbar navbar-default" role="navigation">
<a class="navbar-brand" href="#">Brand Name</a>
<form class="navbar-form" role="search">...</form>
</nav>
</header>
<main role="main" class="page page-main">
<div class="page-heading">
<p>Page Title and breadcrumbs Go Here</p>
</div>
<aside role="complementary" class="page-sidebar">
<p>Page sidebar goes here.</p>
</aside>
<div class="page-content">
<p>Page content goes here.</p>
</div>
</main>
<footer role="contentinfo">
<p>Put copyright, etc. here.</p>
</footer>
Click here to check an example.