Web development is definitely one of the things you are not born with. So, you'll definitely rely on the internet to receive information on web development. Although I find w3schools useful as a quick cheat sheet, I don't feel it's a good place to start learning. Not all of the information is clearly accurate. Their teach methods are not as good too. What is the best web dev school? You're good ol' friend Mr.Google. Google really is your friend. If you need help with a specific area, it can guide you to the best site to teach you that specific area.
I've heard it's not good for HTML/CSS as they use bad techniques and things of that nature. See http://w3fools.com
Okay that site is a little over the top. It has a lot of useful information and it's a great place to reference and even learn from however the best way to do it is by taking techniques from everywhere and trying them. If something doesn't work then you need to learn how to fix it.
For beginners, I think that there are more "in depth" articles that explains stuff a little more and are a little more basic. What I would suggest is just look for "beginner" and "tutorials" and "examples" in google. For example, if your need to know how xyz works, I would look for "xyz tutorials" or "xyz examples" in Google.
w3schools provides some basic information, and it's up to you to upgrade or perfect it. I personally like how it's all organized there.
