The presentation is nice, but I strongly disagree with the author's chosen method of drawing browser icons:

  .browser-support dd:nth-of-type(3) { background-image:url("img/opera-logo.png"); }
  .browser-support dd.no-support:nth-of-type(3) { background-image:url("img/opera-logo-white.png"); }

And looking at the calculated width example reminded me of the box-sizing property [1], which would simplify that particular use case.

[1]: http://www.w3.org/TR/css3-ui/#box-sizing