Nice layout, good use of colours and some really nice script usage. Layout is clean and precise (not clear on what the gallery is showing but minor point). Navigation is interesting and different to most.
Avoid frames; slow loading and poor support. You could achieve all you already have achieved using DIVs but the only thing you really achieve through frames is a loss of search engine support and speed of loading.
Your top graphic is a little slow on loading; maybe losing the frame would help but reducing the image may be better.
Why have everything on a single page? I do like the script for sliding back up but a single page of content with all pages on it seems a little old hat. I find it annoying but not too sure why (aside from dated).
Why the random green tick?
I do like the gallery feature.
In fact I do like the site generally, nice work, and I can see the designer in your site.