Using secure encryption is highly recommended for many websites (for instance, those taking transactions and collecting sensitive user information.) However, in many cases, webmasters face technical issues when switching their websites from HTTP to HTTPS. And one of these issues is the so-called mixed content – e.i. when your secure HTTPS pages include insecure content served over HTTP.
If an HTTPS page includes content retrieved through regular, cleartext HTTP, this weakens the security of the entire page as the unencrypted content is accessible to sniffers and can be modified by man-in-the-middle attackers. For this reason, in many modern browsers, such content might not load, or load with an “insecure connection” warning.
If any of your HTTPS pages have mixed content issues, which means some content on these pages (such as images, videos, stylesheets, and scripts) is loaded over an insecure HTTP connection. Check all the content and try to fix all the instances of mixed content on your pages.
Change all links to point to a secure version of the website.