In Internet Explorer some fields or functions are not working or are rendered incorrectly. The error usually shows after upgrading to the latest Pronestor Room or Pronestor Display for on-premise installations.
The fix was to add a HTTP Response header to the web site with the following parameters:
When installing Pronestor products on-premise, newer version of IE renders local sites in compatibility mode. This can either be override via the fix above, or by adding the Pronestor server to a trusted zone.