Hi Vera. Welcome to justanswer.
Please transfer the images to a computer and check if the images are also having the black shadow or not.
If yes, then the problem is with the CCD sensor. It needs cleaning. The spots are caused by the dust which has got trapped inside the camera and onto the CCD sensor. You will need to get it cleaned.
If not, then the problem is the viewfinder screen.
How old is your camera?
Hi Vera, How did things turn out?