I think I might be interested in using X-Ray Goggles.  It’s interesting that users can look at a web page and see the code behind it.

For my job as a technical writer, and in past professional writing classes, we have had to look at basic HTML and CSS.  I think this is interesting and practical, but I still have a very basic understanding.  X-Ray Goggles does not teach code to users, but it would be helpful in learning it on your own.