It might be for the better, actually. HTML5 and CSS3 are Turing-complete so I can imagine that the moment they would be allowed, some clever marketing company would figure out new and impressive ways to use the new features to scam people. Er. I meant, "provide value-added content".
 - with user closing the loop, see http://beza1e1.tuxen.de/articles/accidentally_turing_complet... for links to an example.
You can do worse with less.
It doesn't belong on that page.
(Hint: basic arithmetic is turing complete if you give it the same affordances)