Yesterday I noticed my autoptimized JS-files were returning an internal server error (CSS worked as that is inlined). My Apache error-log had this entry:
[Tue Oct 13 17:23:42 2015] [alert] [client 178.xx.xx.xx] /var/public_html/blog.futtta.be/wp-content/cache/.htaccess: Option Indexes not allowed here
/var/public_html/blog.futtta.be/wp-content/cache/.htaccess is created by WP Super Cache, which got updated recently, a.o. to disable indexes being created of directories, and the .htaccess indeed read;
# BEGIN INDEX
# END INDEX
The solution? I could have edited WPSC’s .htaccess, but my changes could get overwritten there whenever Donncha would feel like it, so in the end I edited my site’s config in Apache;
And all is well now.