CSS Solved a Big Problem
HTML was NEVER intended to contain tags for formatting a document.
HTML was intended to define the content of a document, like:
This is a heading
This is a paragraph.
When tags like , and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites, where fonts and color information were added to every single page, became a long and expensive process.
To solve this problem, the World Wide Web Consortium (W3C) created CSS.
In HTML 4.0, all formatting could (and should!) be removed from the HTML document, and stored in a separate CSS file.