Copy the complete url of any website, paste it into the wayback machine and if it's trawled and saved it, the webpage will be shown exactly as it was at that date/time.
You can also manually 'snapshot' any page as it is now, and it's saved in perpetuity as it was at that very second, regardless of any editing.
For example, our beloved E-I homepage from 1999:
http://web.archive.org/web/199901250...t-ireland.com/