Want to see what city council was saying 2 years ago? Want to see what the google home page looked like in 1998? Want to browse a web site that has gone off line? Want to find old copies of a document that was posted online? ...Then this is the tool to use.
Just go to Archive.org. enter a URL in the search bar, and click the "take me back button". you will now have a page with a list of various dates. click on a date and you will see what the site looked like on that date, and from there you can browse around.
The Wayback Machine sends robots all over the web taking snap shots of pages, in the same way that google does. While google tries to get the most rerent version of a site, throwing out old copies, the wayback machine on the other hand holds on to these copies, and lets you see old versions.
If you want to learn more about the Archive .org, the group that runs the wayback machine, then check out the following 20 min video. There is only about 1 minute that covers the Wayback machine (at 17:30), but it give sense of what the broader project of Archive.org is about. check it out here:
I will soon put up some more posts on the way machine that look at how to make it useful, and what advanced search features you can put to use to get the most from this tool...