@kurt_der_koenig I have observed you are using .png's on your images. As far as I know .png's has several compatibility issues with IE an in other browsers as well, it fails to display them properly. Browsers of Mozilla on the other hand supports .png images very well.

Try changing your images to .jpg's or .gif's...and see if that works. If your very much concerned about the quality of these images (since you choose .png-less compression) use graphics softwares like photoshop and save it to the maximum quality possible.