My CSS: It all works, but is it *correct* and efficient?

Hello,

I've been laboring over sort of portal page for friends & colleagues, and I used it as a laboratory for creating a tableless layout that works on all v5+ browsers (v6+ in NS). I've got it there, but I suspect that my CSS is probably pretty inefficient and occasionally incorrect, even though it works (mainly I'm thinking of the navigation IDs that are re-used on the same page, something I understand is a no-no, although it's created no problems.

Here's the page:

http://www.hyperarts.com/webstuff/index_test.html

Here's the CSS:

http://www.hyperarts.com/webstuff/webstuff_yello.css

Thanks for any criticisms that lead to a better page and a smarter Tim.

Tim