I've been doing web stuff for about ~15 years, and I was in college for graphic design from 2006-2009, so that was exactly 10 years ago!
As for the web technology we were taught:
I've been building websites during this whole time, and consider myself luck with WordPress getting better over time, but some things, like Flash, which were huge weren't built well, and didn't survive.
There are tons of things you could go out and learn today that would be totally dead, like Flash, in 5 or 10 years, but I know for a fact that HTML, and CSS, and JavaScript will be used, so if you look at core 'foundational' technologies, those are more likely to be 'safe' things to invest time in learning and mastering.
It's also nice that PHP is still king :D Thought your dad might be frustrated, it is also nice that he can keep building on top of knowledge he already has!