Has a designer or developer ever tried lecturing you about why you need to be using proper HTML semantics? If so, did your mind start to wander about 30 seconds into the lecture (is it starting to wander right now)? Do you read the HTML specification to help you fall asleep at night? As long as your site looks good and is maintainable, no user is ever going to know or care if your markup is semantically correct.
Actually, some users with disabilities will know if you're not, they depend on it, and probably can't use your site if you're not using clean, valid, and semantic HTML. Having valid semantic markup helps your site avoid many common accessibility issues. However, in some cases the HTML spec offers several different implementation options or is simply unclear. In these cases thinking in terms of accessibility can help provide direction.
HTML Headings as "Defined" by the Specification
The<h1> - <h6> heading tags are among the most useful and important HTML tags regarding semantics. They define the overall structure of the pages in your site. I hesitate to say they're also among the most misused tags, because the HTML 5 spec is a little ambiguous.
Web Accessibility and Headings
WCAG 2.0 has 2 main guidelines specific to headings. In a nutshell, your content needs to be logically organized into sections. These sections need to have headings, and the headings need to represent/identify the content they're associated with.To further understand the spec and how thinking in terms of web accessibility can help, check out HTML 5 Semantics and Accessibility: Heading Structure.
