CSS or Cascading Style Sheets are what make the Web look great. A little knowledge in CSS can take you a long ways. From background images to drop down menus, CSS is a key component to all websites with any sort of styling.
All of the information that your browser receives about a web page is neatly written in words and symbols that mean something to the browser. Most styling properties of a given web page are words and symbols that identify specific colors, spaces, shapes and images. These are classified under CSS.