CSS is called as “cascading style sheets”. It is mainly used to open and control web pages. It is usually used for controlling web pages which include font sizes, font styles and colour combinations that is necessary for the webpage. CSS files makes changes globally as any change in a CSS file can also lead to an overall change in the website appearance. This means that any change in a certain CSS file can cause automatic changes to the pages that uses that certain CSS file and will display the changes.