I\'m a desktop application developer, and I plan learning html5, but as it\'s not released, there are (almost) no published books and not too much infomation for beginners on th
Get a good base with html/css then move onto javascript and pick a js framework that you like. Jquery seems to be most popular.
Here's a good read on html 5
Another vote for Designing with Web Standards. While not the best "beginner" book out there in terms of holding your hand through your first site build, reading this book is hands down the best way for you to establish a solid foundation of good habits so that when you do get to learning how to code you'll understand why it is important to do things the RIGHT way.
That being said. HTML is cake. Tying it into CSS is a creative challenge, and really being able to understand javascript will set you apart.
As far as technologies becoming irrelevant: Stay away from Flash. Other than that everything is as strong as ever.