Non-existent images being pulled

Hi All,
hope you could help us with a problem.
We have performed the speed test and in the results there are a lot of images that cannot be located on the specific page we were testing. Why can it be happening?

I think, from my earlier experience, it would help if you gave a link to the test.

Have you looked at the images, seen what they look like?

Are they 1x1 pixel images, which would make them beacons doing tracking. ‘Non-existent’ makes me think of these.