Forum:I need a help with some design.

I viewed the source code of a help wikia's startpage.

I found this:

Contributing Everything you need to know about adding content to a wiki.

How can I add styles like that on my wikia?
 * You have to do it through source mode I believe. –  Jä zz  i  21:00, February 7, 2012 (UTC)


 * But how to do so? It's a css file, hence "helptopics" class...
 * Sand Spirit 21:21, February 7, 2012 (UTC)