Since June 10, 2011 AP trading is no longer usable and has been disabled by TJ09 after implementing the new Teleport BSA.
AP trading has been replaced by the Magi Dragon BSA Teleport, a much more effective and safe way to trade. You can choose between two-way trading or one-way transfering of up to four eggs/unfrozen hatchlings. Teleport is currently the only way to trade and has effectively replaced Abandoned Page trading.
On Dragon Cave, users used to trade/gift eggs/hatchlings this way - trading/gifting on the Abandoned Page (AP).
The method used the abandoned code. -> http://dragcave.net/abandoned/CODE with CODE being the egg's code number.
User A (the giver) had to have a fast communication with User B (the receiver), usually via a chat or DC's IRC. User B would be on the http://dragcave.net/abandoned/CODE page. Before the egg was dropped, it would have said, "Try as you might, you can't seem to find the egg/hatchling you are looking for in the abandoned area."
User B typically let User A knew he/she was ready to drop. User A would count down and then abandon the egg, and User B would rapidly refresh that page (usually by pressing the key F5) until User B arrived at the Get Code page, meaning the trade/gifting was successful. If they did not soon reach the Get Code page, that meant the egg was lost and taken by another user.
The AP trading method had been quite risky at times, usually due to communication. Sometimes other users could "snipe" on the trade and refreshed before User B did, resulting in the egg's loss. AP trading varied in success rates based on what kind of egg was being traded. Common or even uncommon dragons had a success rate near 100% if this method had been carried out properly. Rare dragons were harder to trade, though the success rate was still about 85%.