Hi Justin,
I am not sure what do you mean by "given the table name <div id="topic-table"></div>" but my suggestion in these cases is to use tools such as the Chrome Developer Tools and inspect on the page the element which you have styled. By doing so - most of the times, you will find that your CSS rule is included in the page, but it has been overridden by another one. In that case, you can change your own CSS rule so that it takes precedence - worst case scenario you may have to use an !important directive to see it applied (although I would use that as a last resort)
Hope this helps!
To add to what Paolo said, if you have defined a CSS rule within the skin but it doesn't seem to be having any effect, it may be the the rule isn't specific enough (in which case, your rule will get overridden by an in-built Lithium rule).
