Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g., fonts, colors, spacing) to Web documents.

CSS was first developed in 1997, as a way for Web developers to define the look and feel of their Web pages.  It was intended allowing web developers to separate content from design so that HTML could perform more of the function that it was originally based on – the markup of content, without worry about the design and layout.