“Only secure content is displayed” notification in IE

Problem Symptoms:
After switching Aleph OPAC to https:  "Only secure content is displayed" notification in IE

Cause:
Still some content in the OPAC pages are using non-secure content.

Resolution:
* Provide only secure content via https OR
* Switch off the IE as described in this Microsoft article (http://support.microsoft.com/kb/2625928/en-us)

Additional Info
It is a security feature of Internet Explorer that this message is displayed in any case when there are both secure and non-secure content on the page (see http://support.microsoft.com/kb/2625928/en-us). 

There is no way to switch off this IE feature on the server side.