<h1><h2><h3><h4><h5> and <h6>created the document outline. But in the html5
<aside> <article> <section> and <nav>create the document outline as specified. But because of some issue (i think implemention in every single browser or may be something else) it is advised to prefer a way in which both rules are followed. well i covered all this but i cant figure out one thing.