Header inside a header? (HTML5)

Question

This seems strange to me but oddly there is a reason to use a <header> inside a <header>.

With the <hgroup> remove from the spec I'm seem to be at a weird state with what I should/could be doing with a following bit of code.

<header>
    <header>
        <h1>Maecenas faucibus</h1>
        <p class="h1-sub">Donec sed odio dui.</p>
    </header>
    <section>
        <img src="..." alt="faucibus">
        <img src="..." alt="faucibus">
        <img src="..." alt="faucibus">
    </section>
</header>

This does all appear in the header portion of an <article> so I wonder if it does visually appear there then should I still define it as a <header> or should I wrap it all in something like:

<section class="article-header">
    <header><h1>...</h1><p>...</p></header>
    <section>...</section>
</section>

I've not come across anything that said <header> couldn't be nesting inside itself and wondered if this was the same call where you can have <article> nested in itself if it made logical sense (so if something is grouped together makes sense but also still does by itself).

Answer 1

According to the HTML5 specification, it is invalid to have a <header> element inside another <header> element.

It's interesting, because the <header> permitted contents technically do allow for it:

Permitted contents -> Flow content -> Flow elements -> Header

However, there are constraints which are specific to the <header> element - they include:

• The header element must not appear as a descendant of the footer element.

• The header element must not appear as a descendant of the address element.

• The header element must not appear as a descendant of the header element.

Therefore it is not valid mark-up - either as a direct child element or as a descendant element at all.

Answer 2

Looking at the link to the HTML5 specification you just posted (http://www.w3.org/TR/html-markup/header.html) it says..

"The header element must not appear as a descendant of the header element."

Therefore according to the specification it contains flow content but excluding header, footer or main elements.