Well, unfortunately your browser provider has decided not to support the http protocol, and the images are stored on an http website .
Explanation:
http is the original common web language for graphic presentation that we are all used to. Since the nineties, anybody could start a website and if they served content in http on a connected server, anyone else on the web could view and read that content, including photos on any brand of computer, using any browser. A universal language.
Then https came along, That is "secured http" its purpose was mainly to encrypt sales and banking and other pages on the web. It required that the host of the "secured" page purchase a security certificate from another firm. And keep that constantly updated. Security certificates cost money. You couldn't be part of the club without paying someone. This made security certificate issuing firms very profitable.
Then some browser companies decided that all web pages should be secured, whether they were serving sensitive content or not. When directed to any of the old http websites, they put up a warning notice to the viewer saying "This looks bad! This website has bad security information. Do you still want to view it" and if you said yes, well you could see it. You could also make a setting in some browsers that would stop nagging you about it, and just allow you always to view http content.
At first, since the vast majority of older websites were http, particularly small ones that couldn't afford to purchase a new security certificate every year, that feature was an irritation, but not an outright blockade to seeing what you wanted on the web.
Recently that choice was taken away from users of certain browsers. Http websites were simply blocked by these browsers without warning. The claim was "security". However a security certificate does not guarantee anything except that a website has purchased a security certificate. A website could be serving viruses securely, and, no problem, you can still visit with any of the same supposedly "secure" browsers that are presently blocking traditional http websites with valuable and benign content.
Secure https does cause overhead for the Internet, slows communication measurably, causes older computers and operating systems to go obsolete sooner, and makes lots of money for certificating companies, which not surprisingly includes at least one of the largest browser suppliers, as a side business.
If you use that browser, you will not see any http content, including http photos on an otherwise https forum like this one. Why? Photos in forum posts are sometimes hosted elsewhere, off of that forum, and appear in the forum as internal web links. If those photo inks are to an http server somewhere else on the web, the photo simply does not appear in that type of browser. Other browsers will see the photos, depending on whether the user has accepted that he/she can view http content (supposedly "insecure content").
How to solve?. If your browser doesn't allow you to view "insecure" (or more properly, http) content, change its setting, if it has one for this particular issue, or change to a browser that does allow you to.
Note, just because you allow your browser to view "insecure content" you can still also view secure content, and do purchases and banking (if you do those at all) securely, on https pages. It doesn't negate security. And all browsers do indicate visually when they are on secure pages in a number of different ways. You are simply not blocking other http content.
Or if you are worried about it, use two browsers. One for just surfing and information, and a second one, with highly secured features for transactions. That's actually a smarter way of doing them anyway.
