w3c/css-validator — pull request #3 by mirell (2013-06-09 21:35:30+00:00)
Title: Fix Typo on Resolution Units from "ddpx" -> "dppx"

Per the Standard: http://www.w3.org/TR/css3-values/

6.4. Resolutions: the type and ‘dpi’, ‘dpcm’, ‘dppx’ units

Resolution units are dimensions denoted by .
The resolution unit identifiers are:

dpi: dots per inch
dpcm: dots per centimeter
dppx: dots per ‘px’ unit