You can archive your entire website for free, including all of its pages and error pages using https://web.archive.org/. Web Archive has archived over 400 billion websites since 1996. You can even see what google looked like in 1998 (https://web.archive.org/web/19981111184551/http://google.com/). If you archive your website now, it will be permanently archived and in even 10 years you will be able to go back to web archive and see what your site looked like. By archiving your website, if you get in some type of situation where you are not believed to own your website, simply go to an old archive of yours on the Web Archive site to prove it was yours. You can also archive your website to see how much you have improved since the last time you have archived it, or if you are missing data that used to be on your old site. In a short description, Web Archive is like a time machine for the web, to look back at what sites used to look like.