what is the chat box of face-book known as

i am working on asp.net

i want to make a chat room which should be attach like facebook

can any tell me do's and dont's

wht is it called h开发者_如何转开发ow can i start ? designing part ?

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Basic chat using ASP.NET with AJAX: http://channel9.msdn.com/coding4fun/articles/Basic-Chat-Using-ASP-NET-AJAX