I respect the efforts the author put in to teach kids how to program. That being said, I really don't think HTML/Javascript is the right choice for kids. The web stack is even considered messy from professional web programers' perspective. My son will turn seven soon. I did some research on programming languages/kits for kids around that age. I finally settled down on Robomind, which is more or less of a modern varia…
That's a reason I like Javascript. It's not the best language, but you can write something that looks just like any real webpage.
As a kid I never liked software that was kind of like a game with a little programming environment inside: they weren't good games, and they weren't good programming environments.