The CSS Working Group invites implementations of updated Candidate Recommendations of CSS Writing Modes Level 3 and CSS Writing Modes Level 4. These documents define CSS support for various international writing modes, including left-to-right and right-to-left text ordering as well as horizontal and vertical orientations. Level 4 is identical to Level 3, except that it contains the previously at-risk features which were dropped from Level 3 and an additional set of changes.
CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, in speech, etc.
Original source: https://www.w3.org/blog/news/archives/7883