Quite simply put, they help developers make their web-pages beautiful. Think back to some of your favourite websites, and it's a safe bet that quite a few of them have that jaw dropping fancy design. Or, the more subtle, classy kind.

• https://www.codeschool.com/courses/css-cross-country
• https://www.codecademy.com/courses/css-coding-with-style/0/1

• https://www.tutorialspoint.com/css/
• https://www.w3schools.com/css/default.asp