In the html page, we use an h1 component to show a major heading. If we would like to include a subheading below this heading, we would use the h2 element. There are no prizes for guessing that a subheading under an h2 would use an h3 element, and so on, until we get to h6.

The lesser the heading level, the lesser its importance and, as a rule, the smaller (or less prominent) the font.

With headings, an essential (and commonsense) practice is to make sure that they do not jump out of sequence. In spite, you should start from level one, and work your way down through the levels in numerical order. You can leap back up from a lower-level heading to a higher one, given that the content under the higher-level heading to which you’ve jumped does not refer to concepts that are addressed under the lower-level heading. It may be useful to visualize your headings as a list:

>First Major Heading
>First Subheading
>Second Subheading
>A Sub-subheading
> Another Major Heading
> Another Subheading

Here’s the XHTML view of the instance discussed above:
<h1>First Major Heading</h1><h2>First Subheading</h2><h2>Second Subheading</h2><h3>A Sub-subheading</h3>
<h1>Another Major Heading</h1><h2>Another Subheading</h2>