CSS (Cascading Style Sheets) allows separation of design and content of web pages. It was created in 1994 and has become the W3C standard for controlling visual presentation. CSS separates design elements like colors and fonts from the structural HTML markup. This separation allows designers to change the look without altering the content. CSS offers advantages like faster downloads, streamlined maintenance, global design control, and cost savings through reduced bandwidth and higher search engine rankings. Resources for learning more about CSS include w3.org, csszengarden.com, and webmonkey.wired.com.