• Modular Structure: Unlike previous versions, CSS3 is split into separate modules (e.g., Color Module Level 5, Backgrounds and Borders Module Level 3) that progress at different speeds, allowing for faster updates.
• Visual Enhancements: Features like box-shadows, text-shadows, gradients, and rounded corners (border-radius) allow for complex styling directly in code.
• Responsive Design: Media queries allow sites to adapt to various screen widths, enabling better mobile support.
• Animations & Interactivity: Transitions and animations can be created with pure CSS, reducing the need for JavaScript or Flash.
• Layout Capabilities: Flexbox and Grid provide advanced layouts, making it easier to align and arrange elements.

While referred to as “CSS3,” modern CSS is no longer versioned as a single entity.

The W3C now uses CSS Snapshot to organize the current, stable modules.