Just an FYI,
It is bad for UBERCART to cloak the CSS. It is much better to remove the footer text than to have CSS that makes the link invisible. It could actually hurt ubercarts rankings. for more please google, "black hat SEO"
I replied to your other post here: http://www.ubercart.org/comment/11811/mimetic2-wrote. You're not 100% correct, yes black hat is bad, but the only real black hat using invisible / cloaked text are pages that usually have a ton of links on the bottom of the page. These are usually done on what they call gateway pages. Check out more info here: http://www.seoconsultants.com/articles/1007/doorway-gateway-pages.asp
Hiding the footer altogether is different from setting the font's color the same as the background color.