The MDN Web Docs CSS Tutorials is the main CSS learning source for many us. Recently, a new Learn CSS course is available in Google web.dev and was prepared by leading experts Andy Bell, Rachel Andrew, Una Kravets, and Adam Argyle. Rob Dodson and Jiwoong Lee shepherded the UX & production build, along with help from Ewa Gasperowicz and Kayce Basques.
Well deserved — this is great content. Twenty-three chapters taking you through all the fundamentals of CSS with extra content, like relevant podcasts, interactive examples, and even quizzes to make sure you retained what you read.Chris Coyier in CSS-Tricks
This course should a handy reference to learn and use CSS, which we need all the time!