CSS

CSS (Cascading Style Sheets) is a language used for describing the presentation of a document written in HTML or XML. CSS makes websites look good. It is used to style and layout web pages - i.e. change font, colour, size, spacing, add columns, animations and many more.

It can control the layout of multiple web pages all at once. CSS can either be in the same HTML file or they can be stored externally in other CSS files.