Let's first answer your question ...
You could add either of the following to your stylesheet
#craftysyntaxsideboxContent table {width: 100%}
or
#craftysyntaxsideboxContent table {margin: 0 auto}
The former is probably slightly better (plays more nicely with older versions of Internet Explorer)
Now, let's take a look at the template. It's looking like a real SEO killer to me - a classic case of div soup. From column cell to sidebox headings is 11, yes eleven levels of nested DIVs, and when the search engines finally get there, there's no markup to tell them that these are headings.
To a search engine your homepage has a very low content to markup ratio and hardly any structure.