I agree with dab, i feel like i'm looking at a chess board. It needs a bit more life in it than at present.
check out the colour tools in this stickie:
Help me choose the right colors for my website and then living it up a bit.
From a code point of view, very well done. Not sure you need it to be
xhtml, I'm sure
html strict would be fine for a site like this. Which ever one you decide to use, make sure you validate your code against the WCGA tools.
What browser do you use? a couple of good little tools for you:
firefox web developer toolbar
internet explorer dev toolbar
As a customer I would be looking to see the quality of your work striaght away, so maybe a little gallery of your last three sites on the home page would be useful.