The nonsecure warning message in the Internet Explorer browser

If the following warning message is poped up in the Internet Explorer browser:

This page contents both secure and nonsecure items.
Do you want to display the nonsecure items.

the only reason for displaying this warning message is that your page is accessing resources from non-SSL site or locations.

It can happen if you use:
- commercial ads (images, flash animations);
- Javascript code from nonsecure servers (trafic ranking, Google Analytics, etc)

In order to avoid this message remove or change the problem code.