Ultimate CSS Reference

What is this guide?

This guide will be a compilation of several bits about CSS syntax and concepts, so you can read this straight through but meant more as a reference you bookmark and come back to as needed.

What is CSS?

Cascading Style Sheets is a language for defining styles that get applied to HTML pages. This is not a general-purpose programming language (Javascript, Python, Ruby) but like HTML a markup language with a specific purpose, styling (HTML for defining content structure).