I found a site to test with below.
If you use Chome browser on a website, which is https it will but some images are http it will show as an error. ie Not secure content. To say mixed-content
So I like know how to make the spider find for me any contents URLs on a domain which are as http and not https. Mostly images or internal links.
With a domain with 150 pages and 15 sites to check going to be a killed manually checking.
Hope this is clear.