Strange page when pre-viewing the app

Hi guys!  I am developing an app for study purposes so I am not really skillful in Mendix.  Today, when previewing the app this page opened  I have never seen this before and i have never created such a page  can someone help me in deleting it?  thank you :)
1 answers

This is the default sign in page that comes with Mendix after setting the security to demo or production.

The page looks a bit off due to the implemented styling in your app.