Although I always keep a backup of every version of my website, it can be difficult to view previous versions of single pages. For example, to view a stored PHP page I'd need to install it on a web server to view the output, otherwise I'd just see the source code. I'd have to ensure that any external style sheets were in place where expected, and background images restored. All in all, it's quite a complicated process.
Luckily, there's a much simpler alternative. The Wayback Machine, from the Internet Archive has been busily copying websites into their archives for many years. Just enter a URL to see what archives they have for that site. For example, you can see the evolution of my fractals page (note that some images from the early years were not archived, so the page backgrounds were not quite as hideous as they now appear)
Although I built my first web site in 1994, the earliest of my work in the Wayback Machine is the aforementioned 1999 reference.