CSS is a plain text file format used for formatting content on web pages. CSS stands for Cascading Style Sheet and is used by web pages to help keep information in the proper display format. CSS files can help define font, size, color, spacing, border and location of HTML information on a web page, and can also be used to create a continuous look throughout multiple pages of a website. CSS files make it easier for website programmers. It allows a single file which contains all display settings and simplifies HTML by allowing for multiple page layout design.