We will need to phrase this one better.
```
"<p>The css property <em data-highlight='[[cssProperty.start]],[[cssProperty.end]]'>[[cssProperty.property]]</em> has a url() value <em data-highlight='[[cssValue.start]],[[cssValue.end]]'>here</em> that links to an HTTP resource, but the page itself is hosted on HTTPS. Most browsers will not be able to load this resource because of mixed-content restrictions. You will have to link to an HTTPS resource for it to be loaded in your CSS</p>",
```
Particularly the last bit is different because you can't just embed the CSS value in the page anywhere =)