[CSSWG][css-box-3][css-box-4] FPWD CSS Box Model L4, Updated WD CSS Box Model L3

The CSS WG has published a First Public Working Draft of the CSS Box Model 
Module Level 4 as well as an updated Working Draft of the CSS Box Model Module 
Level 3:

     https://www.w3.org/TR/css-box-3/ updated WD
     https://www.w3.org/TR/css-box-4/ FPWD

This module describes the margin and padding properties, which create spacing 
in and around a CSS box. The new Level 4 draft is a copy of the previous Level 
3 draft; all new features since CSS2 have been dropped from Level 3:

   Level 3 = CSS2 + rebase on top of css-writing-modes-3 + more dfn terms
   Level 4 = Level 3 + margin-trim

This split is so that Level 3, with its useful definitions on which a number 
of current CRs depend, can quickly stabilize and be used as a base reference 
for other specs. New feature work will continue in Level 4.

Please send any comments to this mailing list, <[email protected]>, prefixed 
with [css-box] (as I did on this message) or (preferably) file them in the 
GitHub repository at
   https://github.com/w3c/csswg-drafts/issues

For the CSS WG,
~fantasai