Learn CSS fundamentals really fast, online and free. FULL COURSE: http://inarocket.com Learn front end development fast, step-by-step and with ready-to-use code. IN THIS MODULE YOU'LL LEARN: - How to mix selectors (eg. Combine classes and IDs). - How to group selectors as a best practice to get a much optimized CSS. READY-TO-USE CODE: http://localhost/courses/css/css-fundamentals/mix-group.php BEST BOOKS TO LEARN CSS: - CSS: The Definitive Guide: Visual Presentation for the Web by O'Reilly Media. https://amzn.to/2VOWHQT - HTML and CSS: Design and Build Websites by John Wiley & Sons. https://amzn.to/2Ir5y3i - CSS: The Missing Manual by O'Reilly Media. https://amzn.to/2ImdyTf - CSS Visual Dictionary by Independently published. https://amzn.to/2xgwHUh