section

• A generic section (chapter, part, section, whatever) of a document.

• Headings (h1-h6 and header) implicitly start new sections if they're not the first heading in a section.

<section>
  <h1>Validity</h1>
  ...
  <section>
    <h2>Add a Transitional DOCTYPE declaration</h2>
    ...
    <section>
      <h3>Motivation</h3>
      ...
    </section>
    <section>
      <h3>Potential Trade-offs</h3>
      ...
    </section>
    <section>
      <h3>Mechanics</h3>
      ...
    </section>
  </section>
  <section>
    <h2>Eliminate bogons</h2>
    ...
    <section>
      <h3>Motivation</h3>
      ...
    </section>
    <section>
      <h3>Potential Trade-offs</h3>
      ...
    </section>
    <section>
      <h3>Mechanics</h3>
      ...
    </section>
  </section>  <section>
    <h2>Add alt attributes</h2>
    ...
    <section>
      <h3>Motivation</h3>
      ...
    </section>
    <section>
      <h3>Potential Trade-offs</h3>
      ...
    </section>
    <section>
      <h3>Mechanics</h3>
      ...
    </section>
  </section>
</section>