.CSS File Extension
File TypeCascading Style Sheet
Cascading Style Sheet (CSS) file used to format the contents of a Web page; contains customized, global properties for how to display HTML elements; can define the size, color, font, line spacing, indentation, borders, and location of HTML elements.
CSS files are used to create a similar look and feel across websites. They also are used to reduce the amount of work and HTML code generated by consolidating display properties into a single file.
CSS files are stored in a plain text format.