If you want to be a Web devo, you are going to need to learn lots of technologies. That's one of the challenges, and to me, most of the fun, of working with web apps.
And don't underestimate HTML. Everyone thinks it's easy and doesn't need a lot of attention, but it's kind of like chess. You can learn the HTML tags in an hour, but it takes a long time and a lot of practice to learn to use it well -- especially in conjunction with CSS and scripting.
And then there's the whole pool of server-side technologies...