W3C don't validate Viewport

TL;DR

Remove "user-scalable=no" and now the validator is fully ok!

I've found out the purpose of "user-scalable=no", thanks to this answer.

Actually "user-scalable=no" prevents the user from zooming. And it allows the browser to gain 300ms per click.

300ms per click? That's pretty damn good! I should let "user-scalable=no"

But this is no longer the case, according to efheng's answer.

<meta name="viewport" content="width=device-width"> is enough to remove 300ms delay.

Pay attention that any -scale property also triggers that warning

Therefore you should remove all of the following properties, if existent