Let's say aside
element includes "Oh, by the way …" content such as reading suggestions, advertisements, or cross sells.
aside
outside of main
?aside
outside of main
, such as "skip to main content" command?aside
tag outside or inside of main
.In HTML5 it’s only defined that aside
is "related to the content around the aside
element".
In HTML 5.1 (CR) the definition became more specific, as it now says that aside
is "related to the content of the parenting sectioning content".
Following the newer definition, the aside
element should be inside of the section element to which it is related. The main
element is not a sectioning element (elements like article
, section
, body
, figure
etc. are). You can of course still place aside
in main
, but it will be related to the nearest sectioning element parent of main
.
That means there is no semantic difference (for aside
) in these two examples:
<body>
<main></main>
<aside><!-- related to the body --></aside>
</body>
<body>
<main><aside><!-- related to the body --></aside></main>
</body>
Example that shows a few different cases:
<body>
<main>
<article>
<aside><!-- related to the article --></aside>
<section>
<aside><!-- related to the section --></aside>
<blockquote>
<aside><!-- related to the blockquote (not to the section!) --></aside>
</blockquote>
<div>
<aside><!-- related to the section (not to the div!) --></aside>
</div>
</section>
</article>
<aside><!-- related to the body (not to the main!) --></aside>
</main>
<aside>
<!-- related to the body -->
<aside><!-- related to the (parent) aside --></aside>
</aside>
<nav>
<aside><!-- related to the nav --></aside>
</nav>
<footer>
<aside><!-- related to the body (not to the footer!) --></aside>
</footer>
</body>