There are plenty of ways to help your kids learn the basics of HTML. (Im a fan of the no-nonsense videos at Khan Academy.) But when it came to teach my own daughters, they wanted something that seemed a little more fun. Sitting down for a long lecture about angle brackets wasnt going to cut it.

To fill the gap, I wrote Messing Up the Web, a micro-introduction that lets kids start playing and experimenting at the same time that theyre learning how the web works. Heres what you need to know to...