If you have an i18n properties file with an empty value, such as

mykey=myvalue
foo
foo2=bar

then ZK throws a warning with a typo (Igored instead of Ignored):

WARN [org.zkoss.util.Maps] (http-activate.adobe.com/127.0.0.1:8443-1) >>Igored: a key, foo, without value, line 2