Hello Andrew,
I like it a lot. - It's good to see you have used a CSS design and you can not tell that this site is created with DNN. There's only one thing that I can pick you up on and that is you have 2 validation errors on the Home page. - 1st one is caused by using target="blank" which is not allowed in XHTML strict, so you may consider using transitional if you want to use the target statements and the 2nd one is caused by
<div class=leadtxt>
This maybe due to the quotes missing?
I noticed from looking at the CSS code that you have implemented sIFR, this is somthing I'm wanting to implement in DNN but haven't had time to look at, I would be interested to hear any pointers.
I also see that you are importing in a separate list of stylesheets, you may want to consider then removing a lot of the code from the default.css file (you can use CSS shorthand on the default.css file and delete some of the styles to reduce the file size) and portal.css file (apparently you have to leave something in the portal.css file, but you can delete the majority of the content)
Overall looks good and I would be interested in doing an interview to hear your approach of creating this website with DNN.
Cheers,
Lee