Solving the SSL problem “Connection is not secure – Parts of this page are not secure (such as images)”

I noticed once one site with a signed SSL certificate, a message from the Mozilla Firefox browser:

Connection is not secure – Parts of this page are not secure (such as images)

As it turned out, images from other sources were inserted on the site, so the connection can be considered not protected, and to solve this problem, you need to upload images to the current site and change the link on the pages, necessarily starting with https://.

If the site works on http:// and https://, and the pictures are on it, then the links should be changed for example from:

<img src="http://www.ixnfo.com/img.jpg">

to

<img src="/img.jpg">

Done.