ICS file from Web

On our new intranet (running on Ezpublish)we’ve added ics-files for events that are posted. This means that people can click on an ics-file to open it in Lotus Notes to add it to their calendar.

Firefox is our standard web browser, but our users can also use Internet Explorer. If you click on the link to the ics file in Firefox, Lotus Notes tells you that it can’t add open the file, because it’s write protected.

If you click on the same link in IE, it works just fine.

Has anyone any clue to why this happens?