You provide the site a link to a jpeg, hit "process," and seconds later it shows you a goofy side by side comparison that may (or may not) show where a photograph has been manipulated.
From the FAQ:
Error level analysis allows you see to see the difference in quality level, represented by brightness. Things which are very bright have been edited most recently, whilst duller parts have been resaved multiple times. This allows you to see not just which parts of the image have been changed, but in what order the changes occurred.
It shows all my pics have been manipulated, but not really in the right places. I chalk it up to flickr's compression algorithms. Of course, you can also use the site to impress your mom and/or win bar bets.
Anyhow, the site captivated me for a couple of minutes and I thought I'd share.
Same here... I shoot raw and only save the photo to jpeg once.
But, If I were to grab something off the internet and paste it into my picture, for instance (say, a picture of Julianne Moore laying next to me, having my baby), then the pasted in elements will be of a differing quality and that would show.
I'm sure there are other applications as well. For our photos, which are saved only once in their entirety, recompressed in their entirety by flickr, etc, it wouldn't be as helpful.