2.3 #permalink h3 / .h3
Specify a heading level 3. For accessibility reasons, H3 elements should not follow a heading element of a lower level, therefor use the provided class with the same name to apply the visual appearance of a H3 to other elements.
Example
Headline H3
Headline H3
Markup
<h3>Headline H3</h3>
<p class="h3">Headline H3</p>
Source:
typo.css, line 74