There are at least two classes referenced in the "includes/themes.inc.php" that are not defined in any theme's style.css. Those are "albums" and "adm_menu". Are these supposed to be defined? I can't find any themes that define them, but they are referenced in "includes/themes.inc.php".
I found this while trying to reconstruct my theme using the 1.4.2 classic theme as the base (copyied and customized the stylesheet colors).
If the theme looks ok without them, then they don't have to be defined for THAT theme. All selectors are there for the using of theme developers whether they need them or not.