Background

Various projects use invalid markup and use an invalid float attribute (examples)
e.g.
https://en.wikipedia.org/w/index.php?title=Cleridae&oldid=1217116824&action=edit

This is stripped by wiki text and does nothing. We should get these addressed.

User story

As an editor I want to be aware of invalid markup that may create confusion so I can fix it.

float is not a valid HTML attribute and never has been, and this is likely a result of copying and pasting across wikis, expecting it to behave consistently with the align HTML4 attribute which did exist (https://www.w3.org/TR/html4/present/graphics.html#h-15.1.3.1).

We already have https://en.m.wikipedia.org/wiki/Special:LintErrors/obsolete-tag so having a lint rule to flag these issues would be helpful.

Requirements

• Special:LintErrors should flag use of HTML4 or invalid attributes.

Communication criteria - does this need an announcement or discussion?

Communicate to the LintError community that this new rule exists.

Rollback plan

N/A - can be made hidden by default until communities decide to adopt

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