Dots...Alright, fine. A not sarcastic explanation, then. If you look really closely (and with complete disregard for your retinas) you'll see that the elephant figure's dots are spaced just slightly enough apart to give it a different perceived shade but only, as you might have noticed, when you make your eyes readjust to the image after scrolling or looking away.
J-Rod chortled as he came,
Tue 19 Jan 2010, 21:07,
archived)