As far as I remember is LaTeX (or TeX itself) touring complete, too. In the end, if you can simulate a turing machine (or another "equivalent" calculating "device") the language is itself turing complete. While not being a html/css wizard, by the amount of complex examples i saw you could do with only HTML/CSS3, I am not surprised that you can write a cellular automaton in it.
edit: typo (personal hangup with touring/turing)