How can HTTP content be allowed in Safari 9

HTTP content is allowed in Safari 9. If you have a problem, please describe it in as much pertinent detail as possible.

I'm actually having a similar problem. Whenever I try to link up to the wifi at the public library or at school it requires me to log in through a redirected website. The login page seems to be a iframe that suppose to load but ever since I upgraded to "El Capitan" the part of the website that allows me to log in refuses to load. I've logged in through other devices to verify that it was indeed my computer that had the problem. I've done several things like disable the popup blocker, clear cache, clear cookies, try different browsers, clear the history, and reset DNS and no results. I've attached an image of the problem. Thank you

Try another browser as a test.

Firefox