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:
As for the first massive usage, the Wikipedia article on Ajax has the answer:
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...