It is important for all web developers to know something about CSS. This crash course from Web Dev Simplified covers everything you need to know to get up and running with CSS in just over 20 minutes.
It covers CSS syntax, how to add CSS to your HTML, CSS colors, CSS units, the box model, and best practices for CSS. You will see a full example of CSS being used to style an HTML page and by the end of this video you will know enough about CSS to style any basic web pages in your own projects!
You can watch the video on the the freeCodeCamp.org YouTube channel (24 minute watch).