Very similar to an interview process I went through about a month ago. The "full-day" interview sort of irks me. You mention how you were tired, and I imagine a lot of candidates are, 5-6 hours of straight interviewing seems too heavy.
When I had my "full-day" interview it left a bad taste in my mouth. (I ended up not accepting the offer)
> and asked me to write the HTML/CSS for the whole page.
"new release about to be pushed live, and asked me to write the HTML/CSS for the whole page."
I cringed a little at this, but this is not too bad. They probably wouldn't expect you to make it perfect. It is not always the result they want, usually they want to see the process on how to handle working through the problem.
When I had my "full-day" interview it left a bad taste in my mouth. (I ended up not accepting the offer)
> and asked me to write the HTML/CSS for the whole page.
Yowza.