About
The header in html is an element which principal use is to group ancillary information around the top level heading (ie h1).
It may (not required)
- contain the section's heading (an h1–h6 element or an hgroup element)
- wrap:
- a search form,
- or any relevant logos (image)
The header element is not a section element and therefore doesn't take part in the outline algorithm.
Example
Specification's header
<section>
<header>
<p>Welcome! <a href="#">This is home of...</a></p>
<hgroup>
<h1><a href="#">The Falcons!</a></h1>
<h2>Living — Last Updated 19 October 2015</h2>
</hgroup>
<p><a href="#">The Lockheed Martin multirole jet
fighter aircraft!</a> This page discusses the F-16 Fighting
Falcon's innermost secrets.</p>
<dl>
<dt>Participate:</dt>
<dd><a href="https://github.com/whatwg/fullscreen">GitHub whatwg/fullscreen</a></dd>
<dt>Commits:</dt>
<dd><a href="https://github.com/whatwg/fullscreen/commits">GitHub whatwg/fullscreen/commits</a></dd>
</dl>
</header>
....
</section>
Other
<body>
<header>
<h1>Little Green Guys With Guns</h1>
<nav>
<ul>
<li><a href="/games">Games</a>
<li><a href="/forum">Forum</a>
<li><a href="/download">Download</a>
</ul>
</nav>
<h2>Important News</h2> <!-- this starts a second subsection -->
<!-- this is part of the subsection entitled "Important News" -->
<p>To play today's games you will need to update your client.</p>
<h2>Games</h2> <!-- this starts a third subsection -->
</header>
<p>You have three active games:</p>
<!-- this is still part of the subsection entitled "Games" -->