They tried to make the the explicit number irrelevant and infer the level by the number of nested sections, so instead of: <article> <h1>Title</h1>

They tried to make the the explicit number irrelevant and infer the level by the number of nested sections, so instead of: <article> <h1>Title</h1> <section> <h2>Section</h2> <section> <h3>Sub Section</h3> <section> <h4>Sub Sub Section</h4> </section> </section> </section> </article> You could simply use <h2> repeatedly and keep the semantic structure of the former. <article> <h1>Title</h1> <section> <h2>Section</h2> <section> <h2>Sub Section</h2> <section> <h2>Sub Sub Section</h2> </section> </section> </section> </article> However this was never implemented by any browser or screen reader and was finally dropped from the standard. http://html5doctor.com/computer-says-no-to-html5-document-outline/ http://html5doctor.com/computer-says-no-to-html5-document-ou...