Hi Daniel,
hmm, how could i say that ?

MODx hasn’t got the slightest influence on what your website will look like, only your xhtml and css skills will.
(that’s one of the 2/3 main reasons i’ve, at last, after heavily testing this point... accepted to use a cms). Except for some components (snippets mainly) MODx won’t write a single xhtml line for you and, even with those snippets you can write your own chunks to output.
So, sorry to say that but MODx isn’t responsible for ie compatibility issues in the front end (now, having had a look in ie8 and ff, it’s not that ugly in ie

there are only a few rollover issues on the middle menu)
cheer up
have swing