RGB represents colors in CSS. The three streams are namely Red, Green, and Blue. The intensity of colors is represented using numbers 0 to 256. This allows CSS to have a spectrum of visible colors.
CSS was developed to define the visual appearances of websites. It allows developers to separate the structure and content of a website that was not possible before.
Class is a way of using HTML elements for styling. They are not unique and have multiple elements. Whereas ID is unique and it can be assigned to a single element.
With CSS sprites, loading multiple images is not an issue.