Avoid skipping header levels

There have been various discussions in web development circles about whether we can skip heading levels for various reasons, including structural consistency.

Repurposing headers

One of the benefits of a proper and consistent heading structure in an HTML page is that they can be repurposed to improve access to the content. For example, the heading structure could be extracted into a Table of Contents or an outline, providing in-page navigation or overview.

Screenreader users have header navigation, which allows them to go through the document on a header by header basis. It's not perfect, but its very useful to find a piece of information quickly. The screenreader exposes a means of navigation to next or previous headers of a particular level, so a visitor can, for example, jump to the next second-level heading. So far there's no indication of what header levels are available unless the user enquires.

Barriers in skipping headers

This means that if heading levels are skipped they may not be found by a screen reader user. For example, if a screenreader user is navigating down the second level headings (h2), and finds one that comes close to what he's looking for, he may elect to navigate through the third level headings(h3). If this level is skipped in the header structure, the user will be informed that there are no third level headings. Without third level headings, the expectation is that there will be no fourth, fifth or sixth level headings there either. So those headings will typically not be found by a screenreader user.

Skipping a header level makes navigating by headers less usable for screenreader users.