[sirtastic]

Question: Can anyone comment on how important HTML taxonomy in terms of SEO (disregarding accessibility). Will the use of <header> and <article> make any difference in how a page is indexed and ranked directly or indirectly?

One indirect way I can see SEO benefiting is via sharing. Facebook crawling will have an easy time grabbing the <h1>Title</h1> along with whatever comes first in <p>for an excerpt</p>.

Is there any no-brainer reasons or supporting evidence proper taxonomy helps rankings?

[blowski]

I have seen no evidence to suggest that search engines care about HTML5 semantic tags. While the tags may be one particular signal, their algorithms use a lot of signals, so don't rely on markup alone. I suspect if they did give them any value, they would quickly be abused by the black-hats, so they don't bother.

As always, do what's right for your (human) users, and you will eventually get the SEO benefit.

[jordanlev]

Agree with your overall sentiment, but should clarify this:

> I have seen no evidence to suggest that search engines care about HTML5 semantic tags

I think you mean "HTML5 sectioning elements" (header, footer, section, article, aside, main). Because search engines absolutely positively do care about proper "semantic" use of other tags (especially h1...h6).

[stan_rogers]

Don't disregard accessibility. Think of the search engine crawler as a disabled user. The ARIA roles (and many HTML elements have good, sensible defaults) carry a lot of information that a search engine can use as easily as a screen reader can. Good a11y is good SEO.

[retor]

Thing is that wcag recommends following defined web standards, but no screen reader I tried could handle html5 style of relative h-tags, like multiple h1 tags. So if you want to adher to wcag rules, and support screen reader, you need to stick to html4. This will probably change, but in order for us to support screen readers, we ended up with some badly written html5.

As for SEO, my experience is that the big crawlers handle html5 better than screen readers, and that atleast Google puts more emphasis on font size as a measure for the pages h1. "If it looks like the pages heading, people will see it as the h1, so we should consider this a better cue than tags the users don't see" sort of logic.

[stan_rogers]

Outlines are still broken in browsers, yes (so multiple nested-level <h1>s ain't gonna work in <main>), but things like the banner and nav roles work just fine and come free with the appropriate tags.

[ed312]

I wonder if Google should put some time/effort into making a better (ideally free to use) screen reader? They seem to have pretty advanced technology for finding the human-relevant parts of a web page.

[pabloarteel]

Do you have any references to this?

[brlewis]

The first no-brainer that springs to mind is <nav> so that search engines can tell words related to the current page apart from words related to pages you might navigate to.