After uploading the Mittwoch theme files, I've noticed some problems.
The first thing is the limit to how wide the horizontal menu can be before it starts pushing the page wider. The PHP Layers menu doesn't like to share the horizontal space, so to speak. The table it creates will widen to 100% unless it's specified narrower. This is arbitrary since there's no way to know in advance how wide the menu space has to be for any given site, etc. Anyway, I've generally made it 70%, which leaves space for a search box or something.
So I'm thinking about moving the fontsize and color-changing buttons up under the search form so the menu can have the full width of its space.
Another problem is with IE7. There's an error in its CSS file (styles/mittwoch/ie7.css) that causes the right column to be stationary and the middle column to overlap it. To fix this, the "width: 100%" property should be deleted from the #c1c2 selector, at around line 40. I'll upload an updated styles/mittwoch/ie7.css.
The Top Users (user_rank) and Since your last visit (since_last_visit_new) modules have some weird behavior due to background image specification and left-side padding in hover and no-hover states. The fix is a little complicated to post here, but I'll upload a revised style sheet pretty soon (or get styles/mittwoch.css from this site).