First of all, the quoted section is indeed from the 14-year old HTML 4.01 specification. I do not remember ever reading anything of the type in the HTML5 specs. I personally think it was deemed a good remark at the time but has since been obsoleted by experience. Don't forget that HTML4 was the one to actually properly separate HTML and CSS, and as such contains 'mistakes' like the quoted remark that were later 'corrected'.
In essence, there should not be any implicitly locked relationship between your semantic markup and your styling. Like the hX
elements, a div
is also a block level element, but only because of the way it interacts with other elements, most specifically which elements it can contain - an inline element must not contain a block element while a block element can contain both inline and block elements, bar explicitly defined relationships such as ul > li
and table > tr > td
. Essentially the separation of semantics and presentation should be kept so strict that the specifications of the markup language HTML should never even mention the existence of the concept of stylesheets - stylesheets can be applied to anything, not just HTML, and HTML feeds so many more technologies than just browsers.
From a web developer's perspective, you are absolutely right. The block nature of a h4
element merely implies its relationship with potential child elements, and its default representation in the browser's default stylesheet. What the CSS developer then wants to do with his stylesheet is his own choice - for all you care he applies a display:table-cell
rule to it if that properly fits his design.
TL;DR: There is no ambiguity, and you should always write your CSS to conform to how you want to display your HTML, not adapt your HTML to the requirements of the CSS. Using a span
where an h4
is required is just plain wrong from a semantic (and SEO) perspective.