We first need a system to record any invalid HTML, and I would prefer we do not use categories for that but a special page instead.

I am wondering how we will be able to report that error Foo is happening at line XXX, character YYYY.

mr.heat wrote:

Don't make this to complicated. A simple category or special page "ContainsDeprecatedFeature" is enough. Use a generic name so it can be used for everything including deprecated parser functions and such. Add a possibility to filter the special page by namespace if you can. Done.

Start with an empty list of deprecated features. Add one feature at a time. I suggest the <font> tag. Let the Wikipedia community know when that specific HTML tag or attribute will be dropped. I suggest something between 3 and 12 months. The community will do the work.

If the special page is almost empty in most Wikipedia languages add the next feature to the list. I suggest the <center> tag. Then <stroke>. Then <big>. Then <tt>. The last one will be align="..." and valign="..." because it's most used and therefor requires a lot of work to replace. (Note: As explained in bug 40329 it is *NOT* possible to simply replace all align="..." with text-align: ... Replacing such stuff always requires a user to look at the code and to understand what it does. Some replacements can be done with a semi-automatic bot or user scripts. But it never should be done by the MediaWiki software.)

We are currently trying to collect possible replacements: http://de.wikipedia.org/wiki/Wikipedia:WikiProjekt_HTML5 We would like to start but we need a possibility to search for "<font", for example.

My point is that categories should probably not be used as a way to add metadata on articles. Moreover the category table is really huge :/

(In reply to comment #1)

We first need a system to record any invalid HTML, and I would prefer we do not
use categories for that but a special page instead.

How do you envision that working? The benefit to categorization is that you can have "lazy-loading": when a page is reparsed, it can be auto-categorized. How would a Special page work?

I am wondering how we will be able to report that error Foo is happening at
line XXX, character YYYY.

I'm not sure that's necessary.

(In reply to comment #3)

My point is that categories should probably not be used as a way to add
metadata on articles.

Umm, can you expand on this point, please? Categories are _classic_ page metadata, aren't they?

Moreover the category table is really huge :/

And?

MediaWiki-extensions-Linter will create lists of some specific kinds of invalid HTML. And we also have https://en.wikipedia.org/wiki/Category:Pages_using_invalid_self-closed_HTML_tags.

"Invalid HTML" isn't a clear description. Do we want to track anything that isn't adhering to the HTML5 spec? Or what browsers actually implement?