To me at least, mark, details/summary and description lists are not obscure!<p>While I don't code in HTML directly, I write the mark-up in Org mode that exports to those.<p>- My recent blog post where I used mark few times (I have set the mark highlight to be brownish to match my site theme) and also the description lists: <a href="https://scripter.co/hugo-modules-getting-started/" rel="nofollow">https://scripter.co/hugo-modules-getting-started/</a><p>- In some other posts, I use details/summary to collapse large code blocks.
A complete reference to all HTML tags (along with simple descriptions): <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element" rel="nofollow">https://developer.mozilla.org/en-US/docs/Web/HTML/Element</a>
I've found <fieldset> to be immensely useful.<p>For one it lets you create logical groupings and paired with legend give you a header type element.<p>The main bonus is if you add the attribute "disabled" it will disable all the child form elements. Which makes it very simple to lock a form when it's being submitted to the server
For an interesting rabbit hole, read "The Lost Tags of HTML"[0]. It's about historical tags HTML 1.0 through 3.2 that don't exist anymore.<p>[0]: <a href="http://www.the-pope.com/lostHTML.htm" rel="nofollow">http://www.the-pope.com/lostHTML.htm</a>
<progress>, <fieldset>, <datalist>, <details>, and <mark> tags are obscure?<p>Don't tell that to the billion-dollar healthcare company I'm currently building a web site for.
FYI do. not. use. the dialog tag. It may work but it has a host of other issues. I don't even know if it's an accessibility benefit for anyone but it behaves in weird and uncontrollable ways.<p>Just make a dialog with a div like you've always have been.
It is so wonderful to see that <dialog> finally shipped in Firefox 98, yielding full cross-browser support for that feature at long last.<p>That nine year journey was tracked here: <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=840640" rel="nofollow">https://bugzilla.mozilla.org/show_bug.cgi?id=840640</a>
I had no idea about details/summary!<p>I've been using what now seems like a horrible hack, p class="help" to make help boxes that expand on mouseover all this time.
More Obscure HTML Tags in here<p>Link: <a href="https://books.goalkicker.com/HTML5Book" rel="nofollow">https://books.goalkicker.com/HTML5Book</a>