that's because you have the image stored in your internet cache, therefore you get to see it. anyone who is loading it for the first time by not visiting the linked image directly get's an image placeholder because it's smaller than the graphic, and thus is not using up the site host's bandwidth.
... wtf? i just copied the link and pasted it in the little image-y post box like always and ... the rest of that is too much goddamn work. it's a picture of two really cute mice in someone's hand. the end.