I want to learn to develop web sites. What do I need?

I'm preparing to begin another project and find I need to learn a great deal
about developing web sites.
I have a couple of books on my shelf,
*Dynamic HTML, O'REILLY, 1998
*HTML, 3rd ed., O'REILLY, "Covers HTML 4.0", 1998
both are unused.
Should I go with a development package, or just use these books(assuming
they're not obsolete) and use vim or emacs?

Additionally, what do I need to learn if I want to include a purchasing
feature for selling a very few products online?

Do I need to learn XML or other languages/technologies?


Thanks in advance.