Cascading Style Sheets or CSS is a language which is used to describe and create the design and layout within a website or web page. Alongside HTML and Javascript, it is a primary language which is used to create websites or web based content.
CCS includes the instructions to present the content layout, colours and fonts and is linked to an HTML web page seperately which reduces complexity and repetition across the website.
Seperation of a CSS file from the HTML markup of a web page improves accessibility and page load times among the pages that share the same CSS file when cache functions are enabled.
The improvement of accessibility is made possible because of the seperation of CSS files which can present the HTML web page in different styles and rendering methods for print, voice and braile based devices.
With the introduction of smartphones and tablet devices, the CSS language allows for the use of multiple layouts and elements within a HTML web page on devices with different screen sizes.