This hack will automatically add the space required to include your mu admin bar. Add
body {padding-top: 28px !important;}
to the admin bar style and you are done.
Found in the source code of any wordpress.com blog!

I spent the day crawling thru a half dozen articles on utlizing the domain mapping features of wordpress mu. After some angst filled hours, I finally mapped a domain to my Mu site Real Sports Bloggers. For added difficulty, I still use my hostmonster shared account to handle most of my domains. I am running [...]

Site Realign
So if you’re seeing this, then you’ve obviously seen the site realign. Nothing has changed; I just combined a couple pages into one and moved some posts around. I have an issue with the table of contents though. The author of this theme used a nonstandard function to call the pages. It does many [...]