Dive into a comprehensive tutorial on Cascading Style Sheets (CSS) for HTML5 and CSS3. Learn the purpose of CSS, style definitions, conventions, and proper whitespace usage. Explore various methods of defining styles, including link and import elements, as well as personal style sheets. Master CSS selectors, including classes, IDs, pseudo tags, and CSS Level 3 selectors. Understand inheritance, the 'important' keyword, and cascading order. Gain practical knowledge through clear explanations and examples, equipping yourself with essential skills for modern web design and development.