This morning, I came across the following implementation of Rule 110 in pure HTML5 + CSS3 (no javascript). You press tab and space in sequence to run the automaton.
http://elilies.com/rule110-full.html
I looked at the source code, but I really can't figure out how it's keeping track of state. When tab is pressed, I figure that the :focus selectors come into play, but I am not sure what happens when space is pressed.