Please, I want some more HTML

Question

Stack Exchange supports a restricted subset of HTML. In some ways, this is good; but in others, it's a little too restrictive. It would be nice to have the following:

Elements

• <details> / <summary>
• <figure> / <figcaption>
• <ins>
• <mark>
• <small>

Attributes

• lang / <span>

If you want something that's not on this list, please post an answer, then edit the question. (Please remove that last sentence if this question is marked status-completed.)

Answer 1

<details> / <summary>

These elements have many, many uses. See Please add the ability to fold blocks of code in questions and answers (2009).

It would be helpful if <details> supported the open attribute. Ideally boolean-style (<details open>), not XHTML-style (<details open="open">), but I'll take what we can get.

I see no need for the name attribute. Since names are global per-page, and (unlike MathJax) there's no easy way to localise them, that would be a whole other feature request.

Answer 2

Accessibility considerations

Ease for Non-Power Users

Adding new tags may be a great benefit to exprienced users in the know, but for them to be broadly useful, they must also be surfaced in a way that's accessible and easy to use for people unwilling to dig deeply into FAQs and wikis. Otherwise, they'll languish as mostly untouched, regardless of how beneficial they may be.

This might be mitigated by adding new functionality to the editor, or by supporting some level of equivalent Markdown syntax, but wide adoption highly depends on easy, intuitive usage of the new features by the average user.

This shouldn't necessarily stand in the way of adding such new tags, but it should be kept in mind that devoting hours to supporting them probably depends on broad utility.

Further reading

• How do I write an accessible Stack Exchange post? by Mithical
  A brief guide to existing best-practices. Some comments discuss some limitations of the existing markup.
• Tweaking Text Level Styles by Adrian Roselli
  Some research on <mark>, <del>, <ins> and <s>, and their interactions with screen-readers.

Answer 3

<mark>

Sometimes, you're quoting something, and you need to emphasise a particular part of it. On Stack Exchange, <strong> is often used for this purpose.

The quick brown fox jumped over the lazy dog.

(emphasis mine)

However, there's a dedicated HTML element for this! From the WHATWG spec:

The mark element represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context. When used in a quotation or other block of text referred to from the prose, it indicates a highlight that was not originally present but which has been added to bring the reader's attention to a part of the text that might not have been considered important by the original author when the block was originally written, but which is now under previously unexpected scrutiny. When used in the main prose of a document, it indicates a part of the document that has been highlighted due to its likely relevance to the user's current activity.

(emphasis mine)

As per MDN docs:

Don't confuse <mark> with the <strong> element; <mark> is used to denote content which has a degree of relevance, while <strong> indicates spans of text of importance.

Answer 4

<figure> and <figcaption>

Whenever one inserts a block quote into a post, an awkward matter arises: where to put the attribution? It’s not part of the quote, so it can’t be inside the quote markup. But it should also be distinguished from text surrounding the quote: just dumping the attribution line like any other paragraph looks just as awkward.

Correct functioning of security mechanisms depend critically on the evil bit being set properly. If faulty components do not set the evil bit to 1 when appropriate, firewalls will not be able to do their jobs properly. Similarly, if the bit is set to 1 when it shouldn't be, a denial of service condition may occur.

— RFC 3514 “The Security Flag in the IPv4 Header”, §7 “Security considerations”

As we can see, the author of the RFC clearly understands the importance of setting the “evil bit” properly.

One runs into a similar issue when embedding multiple text files in the post and giving names to each of them.

Having the <figure> and <figcaption> elements available will allow attributions and other captions to be appropriately styled, and put those problems to rest.

Previously requested:

• Add Image Captions
• Enhancement Request: Attribution Block Markdown

Answer 5

lang / <span>

The lang attribute makes the screen reader pronounce stuff right, and compensates for Han unification.

In some cases, we can put lang on an <i> tag, but this is not always correct. Adding <span> would make lang a lot more useful.

Answer 6

<ins>

We have <del>. Its counterpart, <ins>, has been maliciously excluded unfairly overlooked. See <del> without <ins>? (2010).

<ins> will probably be abused as underline formatting, but this is relatively minor compared to the terrible things people are already doing for want of semantic HTML elements.