Board Thread:Support Requests - Designing Your Wiki/@comment-32894576-20191127170853/@comment-168424-20191128001059

It is usually best to put CSS you're testing in Special:MyPage/wikia.css and make sure it works before you put it in your wiki-wide CSS page (MediaWiki:Wikia.css).

Besides, you didn't give much useful info on what CSS you changed and where. It makes it harder to help you if we have to guess.