When there’s an error navigating the top-level document or packaged content in an iframe, the app terminates. When there’s an error navigating non-packaged content in an iframe, the app navigates that iframe to the about:blank page unless you provide a custom error page. To create a custom error page, create a file named ms-app-error.html. When a navigation error occurs in an iframe, the app navigates that iframe to the msapp-error.html page and passes the error details as query string parameters. Press the following button to go to "https://www.microsoft.com/nonexistent" in the iframe below and trigger a navigation error.