Manipulating main body, menu and credits

If we take this page as an example (I’m pretty new to CSS so go easy 🙂
http://www.alexking.org/blog/2004/01/25/wordpress-css-style-competition
I like the way the bottom “credits” element goes right across the bottom of the page, and the line to the left of the menu goes all the way down to it.
What I am finding in my own attempts to achieve this is that if the main section of my page (ie posts + comments) is very short, then the menu area with it’s vertical line runs right over that part of the credits area. I’d like to prevent that. Is it possible to
1, force the credits part of the page to stay at the bottom without anything on-top (equivalent to what has been done with the title in that example page)
2, ensure the menu does not fall underneath that credits area
or, more simply, make sure all three main parts of the page do not overlap.
and while I’m asking what does the # mean eg “#header” as opposed to just “.header”, in the CSS.
Andrew