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Consider using the “h1” element as a top-level heading only (all “h1” elements are treated as top-level headings by many screen readers and other tools).

The HTML <h1> to <h6> elements represent headings for the different sections of a document, where <h1> is the highest section and <h6> is the lowest. Headings are specially important on screen readers as they give a quick overview of the contents of the different sections in the web page, so although it’s technically correct (not an error) to use a <h1> in this way:

<section class="about">
  <article>
    <h1>Article heading</h1>
    <p>Lorem</p>
  </article>
</section>

this will raise a warning as it would be preferrable for example to leave the <h1> for the heading of the <section>, and <h2> for the heading of the article, like this:

<section class="about">
  <h1>About heading</h1>
  <article>
    <h2>Article heading</h2>
    <p>Lorem</p>
  </article>
</section>

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