Opera (Windows 10) loads the following image, blinks it on the screen and hides it
When I turn off
Block ads and surf the web up to three times faster
in Opera's settings - the image is shown.
I guess it's an extra to block /ad/ path, many websites arrange the mass of images in subdirectories named as first 2-3 letters of an image or it's md5 hash, just like I do it in very this case.
I checked it out in FF and Chrome - they do not block it.