I got it!
Vanilla has a genuine tag. I inserted another tag 'cause I thought it was an important part of the theme integration. Removing the content-wrap tag solved the problem!
Now the floating as you mentioned :)
- I'm the person who started this discussion, I used a bugmenot account because this one wasn't approved yet :) -
I'll try firebug, but I don't think it's going to find something. I couldn't notice anything strange when looking at the page source.