This article will explain what mixed content is and what you can do about it.
Explanation
If a web page loads HTTPS, yet one of the images, documents, or links to external references is on HTTP this is known as mixed content because some of the content you see is being securely transmitted over HTTPS, while some of it is not. As a result, your browser may block the HTTP (insecure) content or show mixed-content warnings. See Google's Security Blog concerning changes to how they handle mixed content.
Solution
To ensure that sites do not have mixed content, site owners should make sure they use all relative links within their sites and that links to external sites reference HTTPS.
You can Download a Mixed Content Report, Address Items in a Mixed Content Report, and Enable HTTPS by Default to ensure all web content is rendered securely. Please contact our Support Team if you have any questions.