[smitherfield]

I'm sorry if I totally butcher the fundamental concepts of Turing completeness here; I was neither a CS nor a math major.

But as I understand it a Turing machine is a physical impossibility because it is defined as having an infinite stream of data being inputted. And the physical presence of an infinity of information is a physical impossibility (I also wasn't a physics major, so I'm not sure if this violates physical laws or is just a practical impossibility, but either way it's obviously impossible).

So instead of an infinite stream of input, we usually define something as "Turing complete" if it's possible for it perform arbitrary computations on arbitrary input supplied in real time. CSS3 cannot do this; programming languages with real-time I/O can do this.

So CSS3 is "weakly" Turing-complete because it can perform arbitrary computations on arbitrary data input supplied ahead of time. With an infinite amount of random HTML-formatted data input ahead of time (same as a Turing machine), it can be equivalent to a Turing machine. C or Javascript are "strongly" Turing-complete because they can perform arbitrary computations on arbitrary, properly-formatted data input supplied ahead-of-time or in real time.