Using Squid 3.4.5 I observed in cache.log the following warning:
2014/06/08 09:50:42.804 kid1| disk.cc(92) file_open: file_open: error opening file /local/squid34/share/errors/templates/MGR_INDEX: (2) No such file or directory 2014/06/08 09:50:42.805 kid1| errorpage.cc(307) loadDefault: WARNING: failed to find or read error text file MGR_INDEX For other error template files all is well. Marcus