HTML/CSS was designed to be forward/backward compatible and not to be written only for version of Safari installed on dev's macbook. This is against the spirit of HTML.
If I understand right, you are suggesting it is "against the spirit of HTML" to write CSS that isn't backwards compatible... infinitely? You have to draw the line somewhere, right? An ancient enough browser won't support CSS at all. Using only CSS that would be supported by a, say, year 2005 browser would also be pretty limiting.
You can choose to do that if you want, but I think your opinion about the "spirit" is a minority one.
You can choose to do that if you want, but I think your opinion about the "spirit" is a minority one.