The '''[[http://archive.org/web/web.php Wayback Machine]]''' is a section of the Internet Archive (and should '''''not''''' be confused with the Internet Archive itself). One of the most well-known an popular features of the IA, it allows people to see past versions of web pages -- in other words, it's the browser version of a TimeMachine.
Here's how it works: after accessing the WM website through the link at the top of this page, users can paste a URL address on the input-box next to the "Take Me Back" button, and then, after clicking said button, the user is shown a calendar-like list of archived pages (provided there are any). Dates written on blue dots are links to versions of that particular page archived on that particular date.
It's not 100% reliable -- sometimes the particular page or image you remember most fondly will turn out to be missing from the Wayback archive. The site also follows the [[https://en.wikipedia.org/wiki/Robots_exclusion_standard Robots exclusion standard,]] so if your favorite website blocks the Wayback Machine from archiving it in its robots.txt file, then it and its content becomes inaccessible to the public (infuriatingly, if the domain is taken over by a cybersquatter who then implements a robots file, it will also block you from seeing the earlier, legitimate versions of the website). The IA also takes no chances with the law, and so all requests by the copyright owners to remove data from the Wayback Machine are immediately obeyed, so it's not necessarily the best archiving service to stymie an OrwellianEditor.
It's possible to use the IA to instantly archive any given webpage, too -- simply go to the address ''[=http://web.archive.org/save/[url_of_the_webpage]=]'' to save the newest version in the archive.
Our very own Wiki/TVTropes wiki is represented in the Wayback Machine as well, so if you want to see the wiki in its earliest days, give it a spin. It also preserves articles that have been subjected to ExampleSectionectomy or [[Administrivia/PermanentRedLinkClub removed outright]]. [[http://wayback.archive.org/web/20100910084226*/http://tvtropes.org/pmwiki/pmwiki.php/Main/HomePage This link]] leads to the results for the TV Tropes homepage in the Wayback Machine; changing the URL posted to that of the article that interests you, you can access most of the site as it used to be. [[http://web.archive.org/web/20100628221425/http://tvtropes.org/pmwiki/pmwiki.php/Main/SoYeah It's also a good way to]] [[ShowDontTell show (and not tell)]] exactly ''why'' certain articles are now perma-redlinked.
By the way, it gets its name after the WABAC time machine from ''[[WesternAnimation/RockyAndBullwinkle Peabody's Improbable History]]''. [[AndKnowingIsHalfTheBattle And now you know.]]