Board Thread:General Discussion/@comment-33999559-20190604223044/@comment-1038387-20190604225030

The reasons are varied. Some add functionality, some add cosmetic changes. They have to be applies to the .css Mediawiki pages.

Have you read the Help page and explored the Dev Wiki for some ideas and tutorials?

It takes skill and knowledge to write css. If you’re a novice, it’s best to just copy existing code that you like.