In general this is pretty good. One mistake that it doesn't make is to use low contrast for everything. However, the code examples don't look very nice on my box due to the font which comes out as Nimbus Mono L. How about you link to an actual font? (I like Ubuntu Mono, though there are lots of other good programming fonts). Also with respect to code samples, would black text on a white background be a possibuility?
On the font issue: you're effectively saying "I don't like the default monospace font my browser is configured to use, please change your website to fix this" (since Nimbus Mono isn't in their CSS font family list). I feel you as a user have some responsibility in that case.