If I click on one of the “learn more” buttons:
then the CSS seems to load normally after that, even when I go back to the main page. A bit further experiment in Firefox:
This works:
https://kicad.org/
This seems broken:
https://www.kicad.org/
Edit:
Apparently fixed now. 2nd link seems to automatically redirect to the first. (If that is the right way to say it, My web development vocabulary is minimal).