I promise. Those of you who have had their fill should leave now.
So the weird and fascinating thing about this is just how murky things are when you look for correct / best-practice information on this topic. The reason seems to be that the various HTML specifications that have been released are unclear, ambiguous and contradict each other. It seems that everyone has a slightly different understanding or interpretation.
There isn’t much detailed reading material on the subject, but the best I came across can be found here.
There first interpretation is that the heading level indicates the level of importance, but nothing else. There is no implied document ‘tree’ or nested structure. Based on this approach it would be perfectly acceptable to have an H1 midway through the document.
The other interpretation is that headings imply a hierarchical document structure or tree. Therefore although they are technically siblings, and H2 following an H1 indicates a subsection of content within the main heading.
The latter is much cleaner and allows you to focus on providing a clear, organised, well-structured document. It is closest to the natural way you would author other types of document. Personally I find this a much better approach. There are some practical complications as I’ve mentioned recently – you should really have a descriptive H1 as the first thing you encounter in the page, but having worked around these issues the end result is quite pleasing.
In addition this interpretation matches with the XHTML 2 proposed changes that are under debate at the moment. In this model, the hierarchy is made explicit, with nested section elements, and a single h element is indicate a heading at any level. Personally I think have a big nested structure will overcomplicate matters, make it very easy for minor typos to build a drastically incorrect DOM structure, and generally open the doors for user agent bugs. I think bloated, deeply nested documents move too far away from how simple and easy to adopt HTML is, which is the reason for widespread publishing.
