Facebook like inbox

Hi all , iam trying to develope a Facebook like inbox i need all features of inbox. I implemented all using repeater. On left side a repeater when clicked it opens conversations on right side and implemented ajax asynchronous postbook using timer. But the problem is performance i want it same as fb scrolling up and loading messages.. I can post my code sample and db design please help me. What i need is performance and Same scrolling up loading like fb thanks ...