is -negative margin or padding invalid CSS according to W3C?

css, w3c, w3c-validation

Solution

According to Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification - 8.4 Padding properties, negative margin values are valid, negative padding values are not:

Unlike margin properties, values for padding values cannot be negative

Problem

is -negative margin or padding are invalid CSS aaccording to W3C ?

Original source