Those of you old enough to have watched Rocky and Bullwinkle may remember the wayback machine that the dog Mr. Peabody and his boy Sherman utilized to go back in time. There is a similar function on the Internet when a website has changed and you're trying to find info that used to be on the page, also called The Wayback Machine.
A couple years ago, I was trying to find a report that the Bureau of Indian Affairs used to have on the page, but was taken down for some bureaucratic reason. I went to the Wayback Machine, put in the URL, and found what I wanted. Of course, not everything is available, as there are software products out that which will block the Wayback Machine. Still, I've found it to be a useful tool.