I have updated my version of mail.css (along with several other files) to improve the overall look of roundcube.  Most of the changes are very minor, with the overall goal of making the interface more consistant and usable.  I also created more usable screen space, leading to significantly larger message reading and mailbox listing windows. 
    Attached is a zip with all the files that need to be replaced in their proper folders, from the root of your roundcube server.  I have also attached some sample screen shots.  This release has been tested with firefox and IE6 and works properly in both.
    These are all the changes I can recall off the top of my head, there could be more.  Overall, I feel this fastly improves the appearance and usefulness of the default roundcube theme.  I have not modified the Address Book or Personal Settings screens yet, but I will put out a new version that alters those when I get the chance.  For the moment, I have simply focused on the most used parts of the program.

Rob

Changes:
Main Window:
Taskbar menu background image removed, and changed to line up with the other menu icons.
RoundCube logo slightly changed, line below it removed.
Entire interface moved closer to the top of the page after taskbar location changes.
Message count bar moved to bottom of page (its not ideal there, I know, but I can't come up with a better place for it).
Bottom of the page set to be closer to the bottom of the browser window, same with right side.
Message Reading Window:
Message reading pane scrolls within the window, instead of the entire page scrolling.
Composition Screen:
Border colors changed to match the rest of roundcube (Couldn't get the bottom of the message body border to show in firefox, if anyone knows why, please tell me).
Window sizes changed so that even wih CC and Bcc selected, the page will not scroll.