It cannot be the actual size, which is a mere 24.667 bytes. Remember a normal posting also is placed within some wihte space. Do not see that much of a problem there for those that view it, but see what I can do next time, as it is not essential because the code is also clearly given when one clicks the wepawet results,
The fact that it opens in a new window because of its physical size, but now you have edited your post and corrected that fault (27 minutes after my comment), it is fine now ;D
It is the physical size on the page when you expand them 900x600. It isn’t so much any white space placed there by the posting, that is going to be over and above the 900x600 size of the image.