A lot of the CSS properties documented on MDN (reference of all properties available [1]) come with interactive examples, for instance background-color and flex to pick two random samples. There are great introductions to CSS concepts in general on MDN as well (flexbox, grid).

Contributions to MDN are welcome. All you need is an account, and their reference reads more like documentation and less like an ad :)

[1]: https://developer.mozilla.org/en-US/docs/Web/CSS/Reference

> All you need is an account

You can even log-in via GitHub nowadays.

The author of this site is also the author of Bulma (https://bulma.io/) - my goto CSS framework. He's also created another similar site for HTML: https://htmlreference.io/

The first page I looked at, for align-content, says:

The remaing space is 150px

https://cssreference.io/property/align-content/

Also, I lead a fairly ad-free life, so there's way too many ads for me to consider using it regularly - those fixed-on-the-screen ones are especially intrusive. A shame as it looks like a good idea.

I would highly recommend devdocs.io for a cleaner, more extensive documentation reference with no ads and offline support.

I don’t get the 150px things your are saying - what do you mean?

It's a typo: "remaing" instead of "remaining"

Cool, but slow. Couldn't all the data be packed into frontend? Waiting even a sec to check out some property is impractical.

This is really useful - bookmarked.