"Four years later, in 1994, BookLink Technologies featured tabbed windows in its InternetWorks browser... These were followed by a number of others like IBrowse in 1999, and Opera in 2000"

your comment got me curious. It looks like opera was not the one "that invented tabs" after all. http://en.wikipedia.org/wiki/Tab_(GUI)

and XMLHttpRequest came from IE. Do you see where I'm going here?