Invalid iso code stored in /content/myapp/uk/en: e

I am new to Adobe CQ, when i am opening a page from '/content'

GET /content/myapp/uk/en.html HTTP/1.1] com.day.cq.wcm.core.impl.PageImpl Invalid iso code stored in /content/myapp/uk/en: en_uk

is appearing in my logs, how to resolve this ?

I can reproduce your issue by adding a jcr:language property in the /content/geometrixx/en/jcr:content node as shown in the below image, which produces me the below error.

27.01.2017 14:38:46.640 WARN [0:0:0:0:0:0:0:1 [1485549526613] GET /content/geometrixx/en.html HTTP/1.1] com.day.cq.wcm.core.impl.PageImpl Invalid iso code stored in /content/geometrixx/en: en_UK 27.01.2017 14:38:48.337 WARN [0:0:0:0:0:0:0:1 [1485549528325] GET /etc/clientcontext/default/content/jcr:content/stores.init.js HTTP/1.1] com.day.cq.wcm.core.impl.LanguageManagerImpl Invalid iso code stored in /content/geometrixx/en: en_UK

you have to use the correct iso code i.e. en_GB as per the standards.

and also have a look at the Page, PageImpl getLanguage() method for more understanding

After adding the correct code en_GB i can see proper logs without any *WARN* when i access the page

27.01.2017 14:51:44.312 INFO [0:0:0:0:0:0:0:1 [1485550304292] GET /content/geometrixx/en.html HTTP/1.1] org.apache.sling.i18n.impl.JcrResourceBundle Finding all dictionaries for 'en_GB' (basename: ) ... 27.01.2017 14:51:44.343 INFO [0:0:0:0:0:0:0:1 [1485550304292] GET /content/geometrixx/en.html HTTP/1.1] org.apache.sling.i18n.impl.JcrResourceBundle Finished loading 0 entries for 'en_GB' (basename: ) in 31ms 27.01.2017 14:51:44.345 INFO [0:0:0:0:0:0:0:1 [1485550304292] GET /content/geometrixx/en.html HTTP/1.1] org.apache.sling.i18n Service [5690, [java.util.ResourceBundle]] ServiceEvent REGISTERED 27.01.2017 14:51:44.345 INFO [0:0:0:0:0:0:0:1 [1485550304292] GET /content/geometrixx/en.html HTTP/1.1] org.apache.sling.i18n.impl.JcrResourceBundleProvider Currently loaded dictionaries across all locales: [/libs/foundation/components/mobilefooter/i18n/en, /libs/cq/searchpromote/components/pagination/i18n/en, /libs/social/subscriptions/components/hbs/subscriptions/i18n/en, /libs/foundation/components/search/i18n/en, /libs/social/commons/components/hbs/comments/i18n/en, /libs/commerce/components/search/i18n/en]

~Hope it helps