Board Thread:Support Requests - Getting Technical/@comment-38546904-20191010194407/@comment-25014407-20191010201417

The MediaWiki is mainly used for custom styling (.css) or scripts and functionality (.js). I said before that only styling is stored under MediaWiki pages, which is only partially true (before I get corrected on it). Templates are pieces of text or coding that you want to use and/or copy-paste on multiple pages, and they are stored in the Template: namespace, such as Template:Infobox.

Now for your css, a part of it is because the css doesn't use the class  but. I would also recommend PortableCSSPad if you're trying to use custom css to see if it's working. You can also check some classes at Help:Infobox/CSS to see if you have the right ones.