CSS (Cascading Style Sheets) is a language used to make web pages visually consistent. A CSS "stylesheet" contains the details of color schemes, fonts, font sizes, margins, and other features of the web pages that make up a website. Once the CSS stylesheet is created it can be used through an entire website. In some cases, the same stylesheet is used across multiple websites to give visitors the sense that the sites are related or even that the pages are all part of the same website. CSS stylesheets are a powerful tool for keeping web pages consistent. If a change is made to one element in the stylesheet, for example if a color is changed, that color change affects ("cascades through") all the web pages that use that style sheet. All the pages them display the new color.