W3C CSS parse errors

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CSS3

HTML5

I have an error with W3C CSS Validator when I paste my project to check it. I don't know why I got them and don't know what do they mean. And when I paste the code with the error in the direct input, there is no error. Does someone know what going on ? I think it could be vendor prefix but some code haven't so I don't know.

Error (1 line of 17) :

Erreur lors de l'analyse grammaticale. @keyframes fadeout{0%{-webkit-transform:scale(1);transform:scale(1);-webkit-filter:opacity(1);filter:opacity(1)}80%,100%{-webkit-transform:scale(0);transform:scale(0);-webkit-filter:opacity(0);filter:opacity(0)}}

Project website

What I have tried:

Used the css before prefixer and no error, but with prefixer there is still errors