CSS3 (~2009-2012):

Level 3 CSS specs as defined by the CSSWG. (immutable)

CSS4 (~2013-2018):

Essential features that were not part of CSS3 but are already a fundamental part of CSS.

CSS5 (~2019-2024):

Newer features whose adoption is steadily growing.

CSS6 (~2025+):

Early-stage features that are planned for future CSS.

The most popular CSS framework Comparison 2020 

How CSS works: Understanding the cascade

CSS usage on the web platform

With the start of a new season of Game of Thrones, folks are sitting on the edge of their seats waiting to see what’s coming. Unlike the Khaleesi who seems to be going nowhere fast, Node.js Tools for Visual Studio (NTVS) has made some moves recently. Over the last month, we released Node.js Tools 1.0 for Visual Studio, joined the vibrant open source community on GitHub , and created VM images so anyone can quickly get started with NTVS.

CSS is awesome: A dark/light mode switch with preference detection in 15 lines of CSS 

You’ll have 32 levels to go through and solve every challenge by writing the correct CSS selector