CSS is an acronym for Cascading Style Sheet. Files that contain the .css file extension are used to format the contents of an associated Web page. While the CSS file format is most commonly associated with website pages that have been written in the HTML and XHTML programming languages, the format can also be applied to any type of XML document.
A CSS file contains the properties that define how the HTML elements of an associated Web page will be displayed, such as the color, font, size, line spacing, borders and other HTML elements.
CSS files are similar to template files, allowing users to create multiple websites featuring a similar look and feel without having to create each and every site from the ground up.
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