The latest versions of both Firefox and Internet Explorer have enabled a security feature that blocks unsecure (http) sites from being displayed inline in https. Other browsers, including Google Chrome and Apple Safari, also appear to be heading in this direction and will soon require work arounds in updates. As those browsers are updated with this security feature, this Knowledge Base article will be updated.
Below are examples of how this looks and how the viewers to your Sakai site would resolve this in Firefox and Internet Explorer:
In Internet Explorer