Web Making Guides
Filtering items with just CSS and HTMLs
Grid Garden
A game for learning CSS grid layout
CSS Tutorial
W3Schools offers free online tutorials, references and exercises in all the major languages of the web. Covering popular subjects like HTML, CSS, JavaScript, Python, SQL, Java, and many, many more.
Modern CSS Solutions
A series examining modern CSS solutions to problems Stephanie Eckles (@5t3ph), a seasoned frontend developer, has been solving for 15+ years.
Flexbox Froggy - A game for learning CSS flexbox
A game for learning CSS flexbox