@aninotnanau, when a test fails click the red button to see which test(s) are failing and text to help you correct the issue. (Be sure and read more than just the first line of the failing message.)
So reading the entire message it says the img element should use the “display” style property with a value of “block”.
What you have is a div with an id of “img-div” using that value: property; pair.
Also, within your img element why are you setting margin-bottom: 15px;? Something like margin: auto; would be more condusive to centering wouldn’t it?