I don't remember if this was a common technique, but before XmlHttpRequest (came in 2000, i think) we used to do "Ajax" by loading data into an invisible iframe and reading the contents. Worked well iirc.
Also back then (up until ~2005) browsers were hilariously insecure. For example I was in a forum of a local youth club and you could have signatures that were displayed under every post so I added some edgy image linked from my own webserver.
Some day I accidentally put the whole folder on a password protection which prompted the "username password" login window on every page my signature was linked to. FOR ALL USERS.
I realized users would think that the forum software would ask them to log in again for some reason so I basically got all passwords of people in the forum in plaintext on my webserver.
I also don't know how widespread this technique was back then, but I'm shocked this was left out of the article. This phenomenon was literally the method that transformed a "websites" into "webapps" in the early days. We would use pools of invisible iframes to constantly update different parts of the page for a "reactive" experience. The author mentions various important hacks that define the early days, but missing this one seems like a blunder to me.
