CSS3 validation

Question

I have a CSS file that is written in the best style I can. I just tried to validate it and it has about 40 errors. Most of them are like this:

Line 23, Column 3: character "d" not allowed in prolog display: none;

What does that mean? What is "prolog" in a CSS file?

What does this mean?

Line 158, Column 3: this is not an SGML document -ms-text-size-adjust: 100%;

Answer 1

As an older stack question suggests, I suspect you used W3C's html validator when you intended to use W3C's css validator .

Note: CSS validation and cross-browser compatibility are considered mutually exclusive, and best practices demand the latter.