Oh? I've used w3schools for most of my learning although I haven't completely relied on it.
With W3Schools, you'll end up having to unlearn so much, especially when it comes to MySQL+PHP.
In particular, the MySQL+PHP tutorial is based on a terribly out of date MySQL driver (mysql was replaced by mysqli, which was replaced by PDO), which means it can't cover prepared statements. With no prepared statements, it should cover how to prevent SQL injection, but it doesn't. At all. In any tutorial. Tizag is just as out of date, but it at least covers SQL injection, though it's in an "advanced topic" tutorial, which means countless users probably don't bother with it.
It also doesn't go on to cover how to separate data access out of the rest of the system into its own
layer. That's an intermediate topic, but a vital one.
Also, W3School's HTML tutorials don't approach HTML from a
semantic viewpoint. Tizag is a little better on this count, but still measures up short.
HTMLDog might be the best of the three for HTML. It's beginner HTML tutorial doesn't mention semantic HTML (which isn't necessary); at the same time, it doesn't go against the principles of semantic HTML.
There might be other problem areas, and areas where the sites shine. Since I didn't learn by reading tutorials, I've only glanced at what the sites have to offer. I haven't been too impressed, and
I'm not alone. W3Schools is popular, but not good. It persists because that's where people started, so that's what they recommend, not realizing how bad it is.
So I want my first site running as soon as possible.
Patience, young grasshopper. It's better to take a little more time to do it right than do it fast and sloppy. It's harder to unlearn bad habits that learn good ones. If the project were more complex than a comment form, I'd recommend starting as simple as possible and adding features later.