First of all, Stack Overflow is a developer resource and whilst Web Development does come into that you'd be able to find better suggestions and good advice from a real Web Development community. Once you understand HTML and know what development platform you want to use give SitePoint a try. Their forums are a fantastic resource for all web designers/developers and they'll be able to help you a lot more than we will.
Firstly, you'll need to learn about how the Internet works. I'd recommend some light reading on TCP/IP before moving forward. It's not essential information, but it's always nice to know. If possible, find the RFC's for TCP/IP and HTTP.
You'll definitely need to know HTML, and luckily for you there are billions of great websites out there that can teach you the fundamentals. As I've said before on this website Stack Overflow is a developer website and developers aren't the best at HTML or design-related issues. If I were you I'd just search for HTML tutorials on Google and find the best website for you to learn from. I can promise you that someone has already recommended W3Schools and whilst I think it's an awful website you should at least check it out.
If you're going to move into Web Development there are loads of server-side languages to choose from, ranging from:
Again, Google is your best friend on topics like this. Give Google Video a try as well, as a lot of people have uploaded screen-casts to help budding developers like yourself.
Finally, once you understand HTML and know what development platform you want to use give SitePoint a try. Their forums are a fantastic resource for all web designers/developers and they'll be able to help you a lot more than we will.
As far as development environments go you really cannot go wrong with Notepad++. In reality all the IDE's are good enough for web development and any attempt to push you onto a specific one isn't going to benefit you. I'd recommend that you try each and every suggestion here.
Good luck and happy coding!