Get dynamic Web content with HTTPRequest
IBM has an article titled – Get dynamic Web content with HTTPRequest – that will show you how to use the XMLHttpRequest object to facilitate the transfer of data between a web page and a server. This is the same technique that is being used in GMail, Google Suggest, and Ta-da Lists.



Here is a useful link at apple that covers this topic as well:
http://developer.apple.com/internet/webcontent/xmlhttpreq.html