FYI, here is the old German mailinglist thread about that problem:
http://mail.wikipedia.org/pipermail/wikide-l/2003-July/002782.html
In fact the main problem is that absolute:top. Opera doesn't have
problems with width:98%, it was only a design proposition because
article text might reach the right browser window border and thereby
be further right than the blue top bar. But that's not really a problem.
I would propose to remove "absolute:top", make sure that this is no
problem
for all browsers, and then update the wikis.
Daniel