1.Other than guessing, there is no real statement of intent as to what the site is for, so it will just get lost in the hordes of other css sites.
2. The ads chepen the site in a very big way, i had to resist the urge to click away - id consider a more subltle approcah
3. the gap caused by the digg logo looks bad (FF) and could be easily rectified with some css
4. The site, considering it is all about css, is very boring, and easily forgetful, you need to think about why a user would go to you and not somewhere like css zen garden, make your site a css showcase, otherwise it looks like you are simply copying tips from elsewhere.
5. Finally the brand - you have a great domain and you spoil it with a very amateurish logo - consider doing that better - even paying to have it done!