W3Schools and their incredible CSS Library

Anyone who has built a website in recent history knows the importance of good CSS. I myself have been compiling a master CSS sheet that I use on most of the web development projects I'm involved with. I realized that I was trying to accomplish the same set of outcomes over and over, so a standard library of CSS styles was a natural shortcut to a good end.

I know some have been critical of W3Schools.com and their no nonsense way of explaining web development concepts, citing technical inaccuracies and nuances. I've found that those perceived inadequacies either can't be discerned by "normal" people or don't have a discernible impact on the end product. As such, I've been a fan for a couple years now. I've built their site into my Google searches so that I know I'll end up going to the answer that I'm sure they've provided straightaway.

I've used a few of their tools from the CSS section over the last few years, particularly pleased with their tooltip implementation. That's when I discovered that the CSS sheet that they use for their own site, which has all of the CSS needed to implement all of the cool, modern utilities is free to use. They even encourage it!

There are a couple things I like about it:

1. All their examples use this single sheet. I don't have to understand a concept, then look up a different place to find out how to use the W3.CSS framework to implement it. 
2. It uses pure CSS. I only include one CSS reference and I'm good to go. There's no need to import a jQuery/javascript library as well to make it all work.
3. It treats responsiveness and mobile first as the highest priorities. This is what makes simple websites look like websites developed my multi-billion dollar corporations.
4. Templates!

I used one of the templates here. It's one page. I don't host any javascript nor CSS files. Even the icons are used from frameworks referenced and explained by W3Schools.