Minor layout and colour scheme tweaks to improve readability, post separation etc (at least for me :-) ). Based on blenderartists.org from moi@userstyles.

- The page is centred
- There is a grey background (the post background is still white)
- Posts have an orange top border and a background-colour gap at the bottom for better separation (Based on Gez' suggestion)
- User profiles have a grey background
- User profiles have equal padding all around (no extra padding at the top)
- The header is 50px smaller (the logo is cropped a little at the top and bottom, but I like the reduced space usage)
- The forum control links ("User CP", "New Posts", etc.) have a light grey line above and below them and have even padding above and below
- Headings (e.g. for different categories in the forum listings) are larger and black instead of grey
- The edit box for replying to a thread has a white background
- Posts in the post review when replying to a thread are separated with an orange top border and