Board Thread:Support Requests - Getting Technical/@comment-1609742-20130613053715/@comment-5716479-20130619073347

'.js' stands for Java Script, everything with .js extension is used for various scripts.

While '.css' files are used to store styles for your wiki. Every element on your wiki has styles, which are loaded in order.

First is the wikia global style(your theme), which is the same for everyone. Then the your specific css file and lastly you can setup a style with style="something".

It's explained better in that link I linked before. But each theme has it's own file, used only by that theme. If you never heard of themes, then like the majoirty of people you are using the default Oasis theme on wikia.

None of the navbox styles you put in MediaWiki:Common.css (not only the width:100%) is not visible in the oasis theme. You need either move them to MediaWiki:wikia.css or include MediaWiki:Common.css in MediaWiki:wikia.css.

I suggest that you contact support to help you with that. Because from what I seen you might be doing more breaking than fixing.