Stack Exchange is in the process of switching to HTTPS on all sites. As part of this, they have already fixed links to images hosted on imgur (which is where images go if you upload them in a post). At the same time, they stopped showing images that are to other sites and use HTTP in the URLs.
I wasn't clever enough to notice the implications of that before this week's SEDE update, when it would still have been easy to grab a list of affected posts. Now the query is more complicated, but fellow moderator jefromi has created a query that we think finds most of them. This query found 83 images on our main site.
Let's try to fix those posts. Some image links might have rotted since posting (i.e. those images were missing last week too); others exist just fine but at HTTP URLs. The task is to:
Find the image -- if the original URL works, great; if not, try the Wayback Machine.
If the site serving the image works with HTTPS, fix the URL in the post.
If not, decide (a) whether the image is valuable and (b) if so, whether it seems kosher to upload a copy to imgur. (If in doubt about use of other people's intellectual property, don't.) Make appropriate changes to the post.
While you're in there anyway, see if the image's alt text is currently the generic "enter image description here" and, if so, fix that. Alt text is used by people who can't see images, like those using screen readers; the best text is a short, meaningful description of what's shown in the image. If you see anything else you can easily improve (spelling, formatting, etc), please do that too.
I'll post the list of affected posts (according to that query) in an answer. Please move them to the "done" section if you fix them.
Please don't do these all at once. We don't want to flood the front page and push recent posts out of view, but doing ten or so of these at a time shouldn't be too disruptive.