Cascading Style Sheets (CSS)
A computer language used to lay out and structure HTML web pages. In contrast to HTML, which is used to structure a web document and elements such as headlines, paragraphs, embed images and other media, CSS determines the page layouts, colours, and fonts. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple web pages to share formatting by specifying the relevant CSS in a separate .css file which reduces complexity and repetition in the structural content as well as enabling the .css file to be cached to improve the page load speed between the pages that share the file and its formatting.