When you launch a website on SiteSwan, it is automatically issued an SSL Certificate which allows the site to be loaded on a secure, encrypted https connection. That also means that your web browser will show a "lock box" or green check mark of some kind, indicating a secure connection has been established.
However, it is still possible for the website to not be fully secure if you add some non-secure code to it. If you're utilizing our HTML feature, you have the ability to insert code that references other scripts, images, and more, which are hosted on other sites – other URLs. If one or more of those referenced URLs are an http link instead of an https link, or if a referenced URL is an https link, but it is not fully secure, then your browser will likely indicate a "Mixed Content Warning", represented by a yellow lock box icon with exclamation icon, similar to what is below.
Mixed content occurs when initial HTML is loaded over a secure HTTPS connection, but other resources (such as images, videos, stylesheets, scripts) are loaded over an insecure HTTP connection. This is called mixed content because both HTTP and HTTPS content are being loaded to display the same page, and the initial request was secure over HTTPS. Modern browsers display warnings about this type of content to indicate to the user that this page contains insecure resources.
What should you do?
Immediately review any and all custom HTML that you've added to your site. So that means checking every page of your site for HTML posts and also check if any HTML has been added from the "Site Details" page of your dashboard. Look for any references to URLs that start with "http" instead of "https". Most times, it's as simple as changing all of the http references to https and saving your changes.
Now refresh the site and see if the mixed content warning goes away. If it doesn't, then you should remove the custom HTML you've added to restore full security to the site. We would suggest you reach out to the HTML code provider to get further assistance.