Check out example codes for "history of css". It will help you in understanding the concepts better.

Code Example 1

/* Answer to: "history of css" */

/*
  The saga of CSS starts in 1994. Håkon Wium Lie works at CERN – the
  cradle of the Web – and the Web is starting to be used as a
  platform for electronic publishing. One crucial part of a
  publishing platform is missing, however: There is no way to
  style documents. For example, there is no way to describe a
  newspaper-like layout in a Web page. Having worked on
  personalized newspaper presentations at the MIT Media
  Laboratory, Håkon saw the need for a style sheet language
  for the Web.

  Style sheets in browsers were not an entirely a new idea...

  To read the rest of the History of CSS, go check out:
  https://www.w3.org/Style/CSS20/history.html
*/

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