Board Thread:Support Requests - Designing Your Wiki/@comment-1824669-20130106233728/@comment-4018164-20130112192636

Just type in in your wiki's search MediaWiki:Wikia.css and add this code to its bottom part (if you need to do it in the other wiki and you do not have Admin user rights there, you'll need to ask an admin to do it for you).

As RGL mentioned, the text will aslo be transparent. I though it might be fixed by adding another code to select it and give it opacity of 1, but it didn't work (in opacity of 90% the text will still be visibe quite well, though).