Looking for a great, helpful CSS Reference with examples by hand? Try this free, visual guide to CSS!
CssReference.io – a free visual CSS reference
We all know CSS, but do we know all the CSS, with a high level of understanding? Learn (or check something you forgot) by example.
The cssreference.io is a free visual guide to CSS. It features the most popular properties, and explains them with illustrated and animated examples! It’s a really awesome approach, and awesome reference guide.
It covers all the topics, form align-content:
“Defines how each line is aligned within a flexbox container. It only applies if flex-wrap: wrap is present, and if there are multiple lines of flexbox items.”