http://www.archive.org/. This digital library contains millions of web pages which you can locate with the URL. (Sites do have the option to not have their site searched and archived by bots such as the ones used by archive.org, but most do not use it as it would restrict search engines as well. )
So, while you are searching, you find a perfect match but the site is no longer online? Take the URL and pop it into the WayBackMachine. Most likely, you will find your resulting document ready and waiting for you to stop by.