I am certified in Tech Apps, and I have can also teach web mastering as I taught it before you have to be individually certified in it.  In other words, I've taught a lot of web mastering.  I really hate doing it though.

First, I'm not an artist.  Yes, I can look at a website and know it sucks.  I can even design some elementary graphical art if I can find a tutorial that does what I want it to do.

Second, I'm a programmer.  HTML coding is not programming.  It's doing what I am doing now, typing.  It's got a simple set of rules but so does desktop publishing, etc.  Code is at a much higher level and is much more fun.  HTML coding is boring.

Third is projects.  High school students are horrible at long terms, as a rule.  There are exceptions, but the kids that are attracted to a web mastering course do not have the attention span for a long term project.  In fact, CS kids do better if they can finish an assignment in a class period, and thankfully most of the projects in my CS courses are one day projects.

I really admire the people who can teach web mastering and multi-media, BUT give me a math class any day over the tech apps courses.