This CSS module describes how to collate style rules and assign values to all properties on all elements. By way of cascading and inheritance, values are propagated for all properties on all elements.
That summary does this CSS module very little justice. In essence, we are now looking at something that hasn't been touched for a long time in the CSS universe. While cascading and inheritance often does not cause problems, there are times when it screws things up entirely.
Tidy definitions of the CSS cascade and inheritance should allow for more reliable rendering and faster CSS engines.