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It's great having one page sites so you can use JS like crazy but there's always draw backs:
Typically with these types of sites there is a scroll bar visible which suggests scrolling. A user would be more likely to scroll down before using your navigation to jump down the page. This could go against the experience you're wanting to give.
What happens to users with a small screen? It looks like the typical 1024 "fold" will be somewhere around the guy's knee. So then you're definitely doing a combination of scrolling and using the JS menu. The 'click here for a free quote' is also a bit confusing on that basis.
Finally, what happens without JS disabled? I know it's only a few people, but still...
Aside from JS, on the network page what does any of the content here mean? It's a bunch of nice photos of people but what relation are they to you?
On the quote page I love the error styling. The page is clean enough to get away with using these dark styles, otherwise I'd suggest using a brighter redder colour. Basically it's good ;)
Are the drop down boxes going to be JS styled as well?
Finally, a small thing, but perhaps with the 'submit' button there could be something a bit more human with it. "Submit" could be more friendly, or perhaps a 'thank you!' bit of text could be next to the button?
Those criticisms aside the real winner of this design is the simplicity. I especially like the first page.

Thanks Tom, your feedback is very interesting. And i did ask thoses questions when i did my design.
yes i know for the fold ( Not so many people have it but it's ok for a 1024 height screen ). And i know this website won't suit for some browsers ( like ie6 because of png ) and screen sizes, ( like 1024 x 728 ) i assume consciously the fact that my website won't be at its best for some people. Anyway, if i would like to do so, i think i would have to do too many changes that would have kill my comp idea :) May be i'll force the full screen mode.