Since " http://www.css-validator.org/validator" has neither "w3.org" nor "w3c.org" in its domain name, I would venture to suggest that it (http://www.css-validator.org/validator) is not official in any meaningful sense.
Philip Taylor --------
Ok, but you validate with: https://jigsaw.w3.org/css-validator/ I validate my document with: http://www.css-validator.org/validator With jigsaw I know that the problem is the number without unit of measurement, in fact if I add Transition: all 400ms the document is valid. But is https://jigsaw.w3.org/css-validator/ acknowledged as official and valid validator? In many forum lot of people says to follow only http://www.css-validator.org/validator
Ok, but you validate with: https://jigsaw.w3.org/css-validator/
I validate my document with: http://www.css-validator.org/validator
With jigsaw I know that the problem is the number without unit of measurement, in fact if I add
Transition: all 400ms
the document is valid.
But is https://jigsaw.w3.org/css-validator/ acknowledged as official and valid validator?
In many forum lot of people says to follow only http://www.css-validator.org/validator