Now Bel Labs hosts an Ajax Istant Messenger! Have fun with us!
You can try it here…

How Ajax Instant Messenger works?

The XMLHTTPRequest object allows HTTP requests to be sent to the server and get input back from the server. There are two parts to the client-server interaction through this object:

1. The client “pings” the server (a PHP script) for new messages. The server in turn queries a database for any messages for the client, and returns them as JSON. The XMLHTTPRequest object passes this JSON text be parsed by the rest of the JavaScript.

2. The client sends data to the server (a PHP script), such as a new message to another user. This data is then processed by the server (”cleaning” the data of any thing invalid) and put into the database, which is later “pinged” by another client.