User blog comment:BertH/Darwin - The Next Evolution of Wikia/@comment-10797797-20131010110001/@comment-5275700-20131010212638

Fluid layout is a specific type of responsive web design, and is what we decided to go with when exploring different responsive possibilities. By fluid font size, do you mean you'd like to see the font size increase as the layout gets larger?

Special:CSS is specifically set up to edit Wikia.css right now, no other files. When enabled, it's the only way to edit Wikia.css in the default skin. Common.css and other files are still edited in the same interface as today.