Allow progressive enhancement using repeated CSS properties

[marek-saji]

Why?

When a browser doesn’t understand a CSS declaration, it ignores it. That fact is used to do progressive enhancement by specifying the same property twice — if second one is not supported, browser will fall back to the first one, e.g.

p {
  color: black;
  color: rgba(0, 0, 0, 0.5);
}