Here's a few pointers on improving it...
1) Make the pages
valid HTML. This will ensure that everyone will see your site as close as possible to the way you intended.
2) Replace all the images on the splash page and navigation page with the actual text they are supposed to represent. You'll save bandwidth on your end and on the users.
3) Consolidate your navigation page into a smaller bar that is available on every page (except the ones made with iView).
3) Don't link to new pages when you're staying within your own site. Remove all the 'target="_blanK"' or 'target="_new"' attributes from your links.
4) Your pages have a ton of whitespace because you've got multiple tables with 100% height, each taking up one full screen. Consolidate them into a single table, and remove the 'height="100%"' attribute.