I'm using Firefox 3 on mac and you have some alignment issues. I've attached an image - Contact me link intersects with border line and valid css in footer is moving off screen. I also get a white line at the bottom of the page. Probably because of the valid css link though.
You have 1 code error <img src="images/6.png" width="74" height="80" /> (line 71, col 86) needs an alt and you have an extra } at the end of your typography.css file which could do funny things in some browsers.
Reviewing this from a pure visual point of view as I'm still getting to grips with the techie side, but it looks great! Very clear and bold, easy to read text. I love the white part of the page, but not to keen on the brown marbled effect at the bottom, then going into a black gradient. I think the black works, just not sure about the brown.
Was also thinking - does the twitter feed need a headline? It's a little random on the page if someone didn't know that the blue bird represented twitter.
But other than that I really like it, clear, easy to navigate and very professional! Well done