What is CSS2/3?

CSS (Cascading Style Sheets) is a stylesheet language used to describe the presentation of a document written in HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS describes how elements should be rendered on screen, on paper, in speech, or on other media. CSS2 and CSS3 are versions of the CSS standard, with CSS3 introducing many new features and modules, building upon CSS2. They are commonly used for controlling the layout, colors, fonts, and other visual aspects of websites and web applications, separating content from presentation.