CSS WG Blog —
Introducing CSS Values and Units Level 4
Even if the specifications around HTML & CSS develop comparatively slowly, it is still worth taking a look at the website of the W3C from time to time. And so you could recently find a post on a future innovation in the Cascading Style Sheets Working Group Blog: “Introducing CSS Values and Units Level 4“. If you want to stay up to date, you should definitely have a look.