have no clue.. but kinda creepy huh..?

 

when your web browser makes a HTTP request it sends all that information to the server. The server on the recieving end simply knows your IP address because you established a tcp/ip connection with it, making the source address known.



At the other end theres a script/program taking that information and encoding it into a jpeg for your viewing pleasure. Though it looks like you are simply downloading a static jpeg, theres a program on the other end tailoring the output to your specific request.



If you're curious about this stuff, check out the HTTP 1.1 RFC here:

http://www.w3.org/Protocols/rfc2616/rfc2616.html

 

i dont like that guy. hes very angry/green looking now that i think about it.