Have you ever thought about how chatting in Gmail works? I think it works using a programming technique called Comet.
What is comet programming
In web development, Comet is a neologism to describe a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term for multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins
Last few days, I was reading about this technology and thought about sharing the information with you all. Please find the attached sample application which demonstrates how comet works using Asp.Net (Note: Right now it works only in firefox. Fixes or patches to make it work in IE/Safari.. or all the browsers in this world are welcome J )
Please download the demo from here