I fucked up my Chrome Dev-Tools. Why won't Chrome recognize my external CSS file properly on page reload anymore? Instead of filename.css:[linenumber] it is listed as <style></style>

Weird how you say you fucked up instead of google :D

@BambuSource I assume it was something I did, as I didn't have the problem before recently.

Dafuq?!

It turned out to be a space before the ; in one of my SCSS-files which apparently creeped out the final CSS. Although it did validate @ W3C, Google didn't like it.

Check file extension and formatting.
I've changed from UTF-8 to something random and it happened for me too.

@HelloUglyWorld I did have <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> in my header, but apparently I had put the link to my CSS file above it. I suspect it might be closer to the cause than that stupid space-before-; (although fixing that seemed to do the trick)

@haabe I wasn't talking about what's in the file but the file itself.

@HelloUglyWorld aha! Yep, I've experienced that being a problem years ago, resulting in unwanted characters in the beginning of the file. But I don't think it is the reason now. The file encoding wouldn't change from one save to the next.