If you're looking to learn or improve your skills in CSS (Cascading Style Sheets), plenty of resources are available online. Here are some recommendations:

Online Courses:

1. MDN Web Docs: CSS Basics

   • Website: MDN Web Docs
   • Description: Mozilla Developer Network provides comprehensive documentation on CSS basics. It's a great starting point for beginners.

2. freeCodeCamp: Responsive Web Design Certification

   • Website: freeCodeCamp
   • Description: FreeCodeCamp offers a hands-on coding curriculum. Their Responsive Web Design Certification covers HTML and CSS.

3. Codecademy: Learn CSS

   • Website: Codecademy
   • Description: Codecademy provides an interactive learning experience for CSS. The platform offers hands-on coding exercises.

Books:

1. "CSS Secrets: Better Solutions to Everyday Web Design Problems" by Lea Verou

   • Description: Lea Verou shares advanced CSS techniques and solutions in this book. It's suitable for those who want to deepen their understanding of CSS.

2. "CSS: The Definitive Guide" by Eric A. Meyer and Estelle Weyl

   • Description: This book is a comprehensive guide to CSS. It covers CSS2 and CSS3 specifications, making it a valuable resource for both beginners and experienced developers.

Reference Websites:

1. W3Schools - CSS Tutorial

   • Website: W3Schools CSS Tutorial
   • Description: W3Schools provides a comprehensive and easy-to-follow tutorial on CSS. It includes examples and a try-it-yourself editor.

2. CSS-Tricks

   • Website: CSS-Tricks
   • Description: CSS-Tricks is a website with articles, guides, and tips on CSS. It covers a wide range of topics from beginner to advanced levels.

Practice Platforms:

1. CodePen

   • Website: CodePen
   • Description: CodePen is an online code editor that allows you to experiment with HTML, CSS, and JavaScript. You can also explore and fork pens created by others.

2. CSS Diner

   • Website: CSS Diner
   • Description: CSS Diner is an interactive game that helps you learn and practice CSS selectors.

Advanced Topics:

1. "CSS Grid Layout" by MDN Web Docs

   • Website: MDN Web Docs - CSS Grid Layout
   • Description: MDN's guide on CSS Grid Layout is an excellent resource for mastering this powerful layout system.

2. "Flexbox Froggy"

   • Website: Flexbox Froggy
   • Description: Flexbox Froggy is an interactive game for learning Flexbox, a layout model in CSS3.

Remember to practice regularly and build projects to reinforce your learning. CSS is best learned through hands-on experience, so try to apply what you learn in real-world scenarios.