Validation Error Help Options Rating

[BenjiF]

Hi
I'm currently making a website and in the process of validating it through W3C.
I keep getting errors that I do not understand when I do validate it. The errors I'm currently getting are "CSS: box-sizing : "border-box" is not a box-sizing value. [html5]" and "CSS: Parse Error. [html5]"
I have attached the .html file.

Thanks,
Benji.



P.S sorry if I've put this in the wrong place.
EDIT: I uploaded a slightly old version, now the latest.

This post has been edited by BenjiF: May 5 2021, 05:27 AM