Chris Koerner, 05/10/2017 22:32:
[1]https://www.mediawiki.org/wiki/Reading/Web/Projects/Print_Styles#Desktop_Pri...
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