For proper operation, it is important that the website inserted on the post is on the SSL domain (starting with https).
On touchless screens
The webpage is secured in an iframe with a sandbox:
<iframe src="" sandbox ></iframe>
The exceptions are live.com and sharepoint.com due to Office365 links being displayed.
On touch screens
The page you want to display should be customized for such use and the display resolution.
Landscape resolution: 1920x1080px
Portrait resolution: 1080x1920px