I use the Chrome extension KB SSL Enforcer. In the past it has for some reason stopped enforcing HTTPS on this site, despite me repeatedly telling it to. It has always worked fine on all other sites. I tried again the other day and it seems to have stuck. However, the background image (the pattern of holes) was not served securely, so that stopped working (resulting in white background) until I told Chrome to "load unsafe scripts" and my other extension uMatrix to not enforce strict HTTPS. This resulted in Chrome telling me the page was not fully secure, of course. As soon as I did that and loaded again, though, it was full HTTPS, with the background working—maybe the background was cached by Chrome and therefore didn't need to be loaded again?