Proposal
The proposal
Håkon Wium-Lie at CERN, proposed the idea of a style sheet for markup languages on october 10th 1994.
W3C Recommendation
The W3C Recommendation
The World Wide Web Consortium was released in 1996. Bert Bos was influential, and was the co-author of CSS1.
IE5 for the win
IE5 offers full support
Microsoft's Internet Explorer 5 was released in the year 2000, being the first browser to have a full (more than 99 percent) support for CSS1.
The box model
The CSS Box Model
In 2007, the working draft for the CSS box model was accepted, defining the spacings of an HTML element to include margin (outer margin), padding (internal margin), width (of content) and height (of content).