h1

The h1 HTML element represents a heading for the section with which it is associated.

<h1 attribute-name="attribute-value"></h1>

Global

h1 {
    display: block;
    font-size: 2em;
    font-weight: bold;
    margin: .67em 0 .67em 0;
}

h2

h3

h4

h5

h6

Web Hypertext Application Technology Working Group (WHATWG)