CSS is a computer programming language used for describing the visual presentation of a HTML document. It helps separate content and presentation, including layout, colors, and fonts. CSS is one of the cornerstones of the web. Without CSS, web pages would be dull and boring, mostly just white pages with blue links.
One of the fundamental design principles of CSS is cascading, which allows several style sheets to influence the presentation of a document. The "cascading" in CSS refers to the fact that styling rules "cascade" down from several sources. This means that CSS has an inherent hierarchy and styles of a higher precedence will overwrite rules of a lower precedence.
In 1997 web design became much easier thanks to the introduction of CSS. Originally created to separate the content and structure of a web page from the visual design, CSS allows designers to make changes to the visual elements of hundreds of pages by changing one, or a few, lines of code. No longer did a web designer have to sort through each page to change the same code multiple times.
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