SEOpro there is no link in your signature, any chance you could share it with us so that we can learn.
I dont think correct code is the essential point of
SEO as i dont believe there is any single point to
SEO. If there was, then spammers would abuse it but like all other factors im sure it pays a part and I agree that by not giving valid code it can only hinder the robots indexing files.
A couple of sites that you would expect to pay attention to valid code
www.amazon.com 1000+ errors
www.bbc.co.uk 30+ errors
www.cnn.com 40+ errors (Ranked 1 out of more than 2 billion for the word "News")