I believe that w3schools.com is a simplistic, but a very helpful and competently made site, and I will cover the factors that made me believe this opinion.
To begin, obviously no page starts without a home page! Anyways, the home page on w3schools.com is very nice, giving you a functional search bar, and scrolling down gives you a list for places to begin or continue your web-coding!
Now, I went and clicked on the link to the HTML section, and there I was pleasantly surprised. It starts off by immediately giving new users a "try it yourself", where it writes some of the early code, and clicking on it successfully brings the user over to begin writing in their code. On the left, there's an entire list of HTML things to go over, each functioning in bringing the user over to what they click on, allowing you to easily begin where your skillset should find itself.
Now, I've gone through both the home page, and an additional page, and they've all been very functional, but it's nice to take into account some things that could've been incorrectly done while creating this, making validation errors.
There are many, many more out there, and it's a good thing that w3schools.com has accounted for them.
The overall design of the website is good in my opinion, the layout is simplistic, which is good for not catching too much of the attention of people wanting to learn. It's also composed in orderly fashion, which is good for consistency. Overall, I'd give the design an 8/10.
Going along with the design, the usability of the site is also great. It's very informational, and also very diversive, giving the user a sense of freedom. Along with it, the site is great for helping out new html-coders, who may not yet feel confident with using the language. In my opinion, I'd give the usability a 9/10.
In my opinion, I believe that w3schools.com easily fulfills the things it was created for. The design is very user-friendly and accesible, the needed information is found everywhere, the diversity. I would most definitely come back to this site if I ever was in need of information for .html.