From Learn About the Ext JavaScript Library

What is "same-origin" policy

ManagedIframe/ManagedIframePanel Component functionality is degraded when the iframe it manages is not of "same-origin". Todays browsers severely restrict access to the document of a foreign domain (eg. google.com, etc).

Here is a feature matrix of possible events and methods which can/cannot be used as a result:

                      "same-origin-src"     Ext.Updater   "foreign-domain-src"
Listeners: blur              Yes                Yes         No
           focus             Yes                Yes         No
           domready          Yes                Yes         No
           documentloaded    Yes                Yes         Yes
           unload            Yes(except Opera)  Yes         No
           message:subject   Yes                Yes         No
 
  Methods: get               Yes                Yes         No
           select            Yes                Yes         No
           query             Yes                Yes         No
           fly               Yes                Yes         No
           getDom            Yes                Yes         No
           getDoc            Yes                Yes         No
           getBody           Yes                Yes         No
           addListener(on)   Yes                Yes         No
           removeListener(un)Yes                Yes         No
           removeNode        Yes                Yes         No
           sendMessage       Yes                Yes         No
           print             Yes                Yes         No
           execScript        Yes                Yes         No
           writeScript       Yes                Yes         No
           loadFunction      Yes                Yes         No
           getDocumentURI (current document/window.location)
                             Yes                Yes         No (reverts to last MIF.src value)
   
Helper Objects
           CSS               Yes                Yes         No