w3c/css-validator — pull request #2 by mirell (2013-06-09 20:55:26+00:00)
Title: Fix Resolution unit "dppx" typo

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