Thread:Project:Support desk/CSS is not loading properly/reply

I discovered that, indeed, MIME type is related here. When I opened the site in IE and checked the dev tools, I get these errors:

SEC7113: CSS was ignored due to mime type mismatch load.php?debug=false&lang=en&modules=mediawiki.legacy.commonPrint%2Cshared%7Cskins.vector&only=styles&skin=vector&* SEC7113: CSS was ignored due to mime type mismatch load.php?debug=false&lang=en&modules=site&only=styles&skin=vector&* SEC7112: Script from http://********/load.php?debug=false&lang=en&modules=startup&only=scripts&skin=vector&* was blocked due to mime type mismatch Special:Version SEC7112: Script from http://********/load.php?debug=false&lang=en&modules=skins.vector&only=scripts&skin=vector&* was blocked due to mime type mismatch Special:Version SEC7112: Script from http://********/load.php?debug=false&lang=en&modules=site&only=scripts&skin=vector&* was blocked due to mime type mismatch Special:Version

How can I ensure that load.php is serving the CSS MIME type properly? In mime.types, it lists "text/css css", so I'm not sure what else I can do.