The section tag represents a generic document or application section. A section, in this context, is a thematic grouping of content, typically with a heading. Examples of sections would be chapters, the tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site's home page could be split into sections for an introduction, news items, contact information.
Example:
<section> <h1>Twitter Section</h1> <ul> <li><a href="http://twitter.com/W3C">Twitter</a></li> <li><a href="http://identi.ca/w3c">Identi.ca</a></li> </ul> </section>
<header>
The header tag represents a group of introductory or navigational aids. A header tag is intended to usually contain the section’s heading , but this is not required. The header tag can also be used to wrap a section’s table of contents, a search form, or any relevant logos.
Example:
<header> <h1>Rob’s Awesome</h1> <p class="tagline">A lot of effort went into making this effortless.</p> …
</header>
<footer>
The <footer> element specifies a footer for a document or section.
A <footer> element should contain information about its containing element.A footer typically contains the author of the document, copyright information, links to terms of use, contact information, etc.You can have several <footer> elements in one document.
Example:
<footer> <p>Posted by: Hege Refsnes</p> <p><time pubdate datetime="2012-03-01"></time></p>
</footer>