Refused to display 'http://extremedev.example.com' in a frame because it is set 'X-Frame-Options' to 'SAMEORIGIN'
This is an error that can appear when you want to display a site through an iframe of another site. It will not allow for the site within the iframe to be displayed.
So what to do in this case?
There are several articles on the internet that are suggesting that you need to add some headers that will allow the display of the site through the iframe from different domains. For example: https://developer.mozilla.org/en-US/docs/Web/HTTP/X-Frame-Options