When you try to change a meeting in a public folder by using Outlook on the web (formerly called Outlook Web App), you receive the following error message:
Error: Public folder meetings cannot be modified in OWA.
It's unsupported to use Outlook on the web to edit meetings that contain one or more attendees in public folders. However, using Outlook on the web to edit appointments in public folders is supported.
To make changes to meetings in public folders, use Microsoft Outlook.