Sometimes the generic page footer (<td id="footer"> and background-image:
url(${rootURL}/images/hudson.png) in
main/core/src/main/resources/lib/layout/layout.jelly) can get in the way of page
layout. I will attach a screenshot of the config page for one of my projects, on
Firefox/Gnome, minimum font size set.

I am especially suspicious of the arbitrary-looking 70% in

<table id="main-table" width="100%" height="70%" ...>

but maybe something else is to blame.