The httpd dæmon on OpenBSD uses the following stylesheet for all of its error messages, which presumably covers all the Comic Sans variations on non-Windows systems:
http://openbsd.su/src/usr.sbin/httpd/server_http.c#server_abort_http
810 style = "body { background-color: white; color: black; font-family: "
811 "'Comic Sans MS', 'Chalkboard SE', 'Comic Neue', sans-serif; }\n"
812 "hr { border: 0; border-bottom: 1px dashed; }\n";
E.g., try this:
font-family: 'Comic Sans MS', 'Chalkboard SE', 'Comic Neue', sans-serif;