Board Thread:Support Requests - Getting Technical/@comment-876677-20151218105403/@comment-26843745-20151218114736

I highly doubt it is possible, really. People other than you can not see it because a personal CSS is supposed to work for its owner only. If you want all users to be able to view certain CSS changes, then you should use MediaWiki:Wikia.css, that is if you are an administrator on that wiki.