element.style isn't a CSS selector. It's a Firebug indicator of styling that's being applied directly on an element through HTML or JavaScript. So you'll need to find the actual element that you want to style, add a CSS class to it if necessary, and style that (possibly with !important to force an override). Unfortunately it may require a lot of trial and error to get it right.
I ran into something similar and Joe helped me in this thread.
Jamie