The websites that implement Ajax are from Google. They are orkut, Google Suggest, Gmail. I played with Google Suggest to find out how they have built. I am presenting what I learnt:
This request would return a result like this:
sendRPCDone(frameElement, "google", new Array("google", "google.com", "google toolbar", "google maps", "google scholar", "google mail", "google images", "google tool bar", "google map", "google uk"), new Array("155,000,000 results", "1 result", "3,170,000 results", "6,890,000 results", "2,210,000 results", "20,600,000 results", "21,500,000 results", "3,460,000 results", "10,500,000 results", "16,300,000 results"), new Array(""));
What has happend is that the server has processed the request and has sent a response back to the client. Here the Ajax engine (function qc(ac)) is responsible for sending the request and handling the response. Once the response is received it refreshs the view.
Its just amazing to see how some primitive time tested technologies if used in a certain combination could make the line between the thin and thick client so thin!