CSS 3 CSS is style sheet language describing document's (typically written in HTML) look and feel. CSS 3 is the latest version of the language, that brought in many new and exciting features developers have been waiting for since 1998.

Cross-browser compatibility for features, that previously were implemented using prefixes or ugly hacks, was one of the most important points of the update. The new standard consolidated implementations of things like font shadows, box shadows, gradients, media queries, new selectors, namespaces, etc.