CSS3 is the third major version of the cascading style sheets web standard. Unlike its prior version, CSS2, it is divided into various separate documents called “modules.” Due to modularization, different modules have different stability and statuses. Furthermore, each module adds new capabilities or extends features defined in CSS2, preserving backward compatibility.

It introduces new features for responsive design and for applying a massive range of content customization. It allows the developer to implement a range of styling features like font, colors, borders, and many more elements to web pages.