>6. Ad-exchange receives all the bids and picks the second highest bidder (no idea why it's the second highest)
>7. Ad-exchange then sends this second highest bidder's ad URL back to the waiting javascript running in the users browser, and ad-exchange marks the winning bid so it knows who won/who has to pay at the end of the month.
It's a second-price auction - the highest bidder is picked, but the second-highest price is paid (more or less). The URL thus is from the highest bidder, not the second highest bidder.
It's a second-price auction - the highest bidder is picked, but the second-highest price is paid (more or less). The URL thus is from the highest bidder, not the second highest bidder.