I'm trying to understand the origins of AJAX, and think MSXML and XMLHTTPRequest were the objects that started it all.
Which came first, and/or became the defacto way to create dynamic pages?
For the origins, see Wikipedia's XMLHttpRequest article, particularly this excerpt:
The concept behind the XMLHttpRequest object was originally created by the developers of Outlook Web Access (by Microsoft) for Microsoft Exchange Server 2000. An interface called IXMLHTTPRequest was developed and implemented into the second version of the MSXML library using this concept. The second version of the MSXML library was shipped with Internet Explorer 5.0 in March 1999, allowing access, via ActiveX, to the IXMLHTTPRequest interface using the XMLHTTP wrapper of the MSXML library.
As for the first massive usage, the Wikipedia article on Ajax has the answer:
The utility of background HTTP requests to the server and asynchronous web technologies remained fairly obscure until it started appearing in full scale online applications such as Outlook Web Access (2000) and Oddpost (2002), and later, Google made a wide deployment of Ajax with Gmail (2004) and Google Maps (2005).
I am sure there are other examples, but personally the example of Gmail strikes home. I never used Outlook Web Access, but I clearly remember the first time I gained access to my Gmail mailbox. At that time I really was wondering how they achieved that without iframes...