People on this board have talked about programming as a gear in your brain that, to a first approximation, you have or you don't. I'm wondering if there's some well put-together resource you can direct someone with zero experience and just a web-browser to and say "if you're having fun an hour from now, you have the gear, good luck" -- maybe something on Khan academy?
(I learned to program a long time ago, and I started with BASIC program listings in my math textbook -- I don't actually know what the optimal onramps are now.)
If there is a site that will let you play with strictly-validated HTML or something like that, I think that could be a good introduction to the idea of precise syntax without having to worry about algorithms or variables at first. But I agree that typically HTML is a bit too loose.
In fact now that I think about it, teaching syntax and semantics separately (eg with a stricter subset of HTML for the first and some sort of graphical programming thing like Scratch for the second) could be helpful for beginners.