Forum:Table background works in Monobook but not default skin

I am trying to make a template that uses a background image in the header cell. (w:c:Sryth:Template:ResUpgrade) I have the image defined in w:c:Sryth:MediaWiki:Common.css as a class called wood. It displays correctly in Monobook, but not in the default Wikia skin. Do I need to add it to Wikia.css as well? What is the problem? Thanks! Psychoadept (talk) 23:21, October 3, 2012 (UTC)