I'm trying out the Napa tools in Office 365 preview, and I'm deploying the out-of-the-box sample app to my site. It displays fine in the Napa preview window, but within my site that app part shows "This content cannot be displayed in a frame." (Using IE10.)
I found the following KB article: http://support.microsoft.com/kb/2643142 but the resolution it gives is not practical. If I have external users I can't expect them to change their browser settings.
Is this a limitation with all Sharepoint 2013 apps or just with Napa apps?