The styles are hardcoded in debug.xhtml. I think your only option is to update that file in your jboss-seam-debug.xhtml.
FWIW, the debug page looks great on every browser I've used. If it doesn't look good somewhere, perhaps you can suggest a better default style to use.
ok, thx I see it. I'm referring to the font in the stack trace (exception) portion of that debug screen.
it's really a minor point...