Thanks for the reply. Yes I have. Just prior to typing this reply, I fired up Google Chrome 18.0.11025.151. Very nice appearance. No graphics/visual problems there at all.
I take your point that Firefox should look good regardless of the platform. This I verified in my original posting, viz-a-viz, Firefox 9 on Windows 7.
As you say these problems sound more like graphics glitches, do you think the Nouveau driver in Firefox 15 may be the problem ?
I just typed nouveau into KPackageKit. It returned one package with a green tick beside it. So the only package/driver it could find is already installed.
Where to from here ? Ahh, the joys of learning.