W3C

First Public Working Draft: CSS Box Sizing Module Level 4

The CSS Working Group has published a First Public Working Draft of CSS Box Sizing Module Level 4. This module extends the CSS sizing properties with keywords that represent content-based “intrinsic” sizes and context-based “extrinsic” sizes, allowing CSS to more easily describe boxes that fit their content or fit into a particular layout context. This is a delta spec over CSS Sizing Level 3.

CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc.