Guess the number!!!!!!!!!!

I got this mail from Jagjit, which had a link to this site - http://www.quizyourprofile.com/guessyournumber.swf

I found it quite amazing and all efforts to decipher the trick failed. Can any one help me out with the possible explanation. I thought it was something like the card tricks where five or six cards are shown to you in one slide, and then you are asked to select one of them. In the next slide, your selected card get's removed, trying to prove it magical. However, on close observation one realises that in fact, all the cards have been changed!!!!!!!!!!!!!!!!! Voila.