2.4 #permalink h4 / .h4
Specify a heading level 4. For accessibility reasons, H4 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 H4 to other elements.
Example
Headline H4
Headline H4
Markup
<h4>Headline H4</h4>
<p class="h4">Headline H4</p>
Source:
typo.css, line 106