[ProSkinner.com]

If you could add "html " before all vBulletin classes, it would get the job done and successful override your custom CSS. (e.g. changing .tcat { } to html .tcat { } would force override any inherited CSS, which is the problem you're facing. Because vBulletin's existing CSS definitions can't be renamed, you won't be able to do that.

My suggestion is to edit your custom CSS and remove any conflicting tags. For example, if you have a definition called div#header or div.header, you should remove the "div" part or anything before the # or dot.