Chris Koerner, 05/10/2017 22:32:
This and <https://phabricator.wikimedia.org/T173909#3548401> do not
provide much clarity, at least to me. If there are some
recommendations/requests for local CSS/HTML styles or for content, they
should be documented in an approporiate manual or help page, for instance:
<https://www.mediawiki.org/wiki/Manual:Interface/IDs_and_classes>
Nemo