h3

The h3 HTML element represents a heading for the section with which it is associated.

<h3 attribute-name="attribute-value"></h3>

Global

h3 {
    display: block;
    font-size: 1.17em;
    font-weight: bold;
    margin: 1em 0 1em 0;
}

h1

h2

h4

h5

h6

Web Hypertext Application Technology Working Group (WHATWG)