You have an image in your epub that doesn't have a valid address for the source document. You can not point to an image on a webpage or your computer, it must be
in your epub.
A valid location should look something like:
<div><img alt="" src="
../Images/MyPic.jpg" /></div>
... where MyPic.jpg is located in your "OEBPS/Images" folder of the ePub. If the image is located somewhere else in your ePub, then give it that path.