...i know the new logo for google has been around for a couple of weeks now, but on their uk site if you do a search e.g. http://www.google.co.uk/#hl=en&sour...4g3g-s1&aql=&oq=&gs_rfai=&fp=234c7fdfc3f9c4f6 and save the logo, or view it, you'll see this: interesting, huh?
It's a pretty common technique used by web designers. One background image to download and use positioning to display the part of the image you want.