LESS - The dynamic stylesheet language

LESS is a dynamic stylesheet language, it extends CSS with dynamic behavior such as variables, mixins, operations and functions.
LESS runs on both the server-side (with Node.js and Rhino) or client-side (modern browsers only).

As an extension to CSS, LESS is not only backwards compatible with CSS, but the extra features it adds use existing CSS syntax. This makes learning LESS a breeze, and if in doubt, lets you fall back to CSS.