There are six levels of heading, with ' h1 ' being the most important (hence the largest) and ' h6 ' being the smallest.
The HTML
<h1>Heading 1</h1>
<h2>Heading 2</h2>
<h3>Heading 3</h3>
<h4>Heading 4</h4>
<h5>Heading 5</h5>
<h6>Heading 6</h6>
There are six levels of heading, with ' h1 ' being the most important
(hence the largest) and ' h6 ' being the smallest.