https://caniuse.com/ https://caniuse.com/ is also invaluable to check whether the cool CSS feature is actually supported. it's very much today's quirksmode.com.

https://caniuse.com/ https://caniuse.com/ is also invaluable to check whether the cool CSS feature is actually supported. it's very much today's quirksmode.com. Once upon a time I would have recommended Eric Meyer's CSS Definitive Guide without hesitation (I think I still have my 1st Edition copy) and it looks like he's re-released with updates for flexboxes and grids.