Matt is an actor and producer by trade, and a fan of wiki as a hobby.

Sites running PmWiki that I have contributed to:

CSS Suggestion for

  (your overall site content, including non-content background color)
body {
   margin: 0 auto;
   width: 780px; (pick your own width, but yours looks like ~800px)

The above should center your page in the middle of the browser window.