Click on the header of the main Home page. In the "properties and action" window click on properties tab. scroll down to you see "Inheritance from master page" make sure it is set to "yes". Now go to the header of each devices or page group and repeat the above steps. You can set the default font, menu keys, funtion keys, and channel keys this way or you can turn off the inheritance so a page collection can be setup with it's own settings, say for a zone 2.