I decided to create maximally backwards compatible website, so it should work on legacy systems (including old IE), and smartphones using responsive web design. I know that CSS was gradually implemented in previous versions of browsers, but I can't find information (reference) about CSS features supported in previous versions of popular browsers. What is the best website or a book that describe the chronology of CSS implementation?
Reacher; You Can't Go Back
There were two major breaks that make that goal difficult to reach: 1) IE finally moved into this century; and 2) both HTML and CSS had major revisions.
W3C also made the Mozilla Developers Network (MDN) its official reference. This is a good thing, as tutorials and browser support are included.
See https://developer.mozilla.org/en-US/docs/Web/CSS
https://developer.mozilla.org/en-US/docs/Web/HTML
gary