Hi,
In IE11 and older, IE is lost, disoriented if the image extension is not corresponding to the inside format.
For ex: "image.jpg" but inside, it's a png format.
Edge/Chrome/Opera/Firefox/Safari don't rely on the extension, but on the real inside format.

So, sometimes in this forum, the avatar is not displayed (see attachement).
Ex: "https://www.concrete5.org/files/avatars/4.jpg" but inside is : "‰PNG ...."

Nb: this issue is not only in this forum, but on all websites.
Solution : always have the right extension for the inside format.

Thanks,
Max