What is Mixed Content?
Many websites suffer from mixed content. A mixed content warning can happen in browsers when a web page loads assets over HTTP when all loaded assets should be loaded over HTTPS.
Most web pages are made up of HTML and then a number of different assets. Assets are pieces of content that are loaded separately to the rest of the web page. Examples of assets are images, videos, stylesheets and JavaScript files. If your website is loading over HTTPS using an SSL certificate (which it really should be) but any of the assets on that page aren't using HTTPS then your visitors will encounter a mixed content warning.
How Browsers Handle Mixed Content
Different browsers treat mixed content differently, but most of the mainstream browsers (Chrome, Firefox, Edge/Explorer and Safari) will show the user a warning of some sort, either in the address bar on, in some cases, even more prominently. You should avoid having mixed content anywhere on your website. Browsers are getting stricter with HTTPS-related features with every release, so it's really important to ensure your entire website is free of mixed content.
Your Visitors
Any browser warning is a big no-no for your visitors, but when it involves security then it's even more scary. Most browsers will mention security of the web page when showing a mixed content warning, and the urgency of the messaging is usually quite severe, although that does vary from browser-to-browser.
A warning of any kind is bad for your visitors, but if your website is a transactional one that requests visitor details (perhaps via a contact form) or even takes payment then it is likely to put your visitors off and could cause you to lose a lead or sale.
Janitor's Check
Janitor will crawl your website at least once per day looking for mixed content. The depth of the crawl depends on the plan you're on, but we'll visit as many pages as we can, and our crawler follows the page's hierarchy to work out the most popular and important pages on your website, prioritising those over the less popular pages which are often found deep within the website.
If any mixed content is found on the website Janitor will tell you what page the asset was found on, what the URL of the problematic asset is, and even what HTML tag the asset was found on. This information will be enough for you or your developers to fix the issue quickly and easily.