Alf Eaton sent me a note about WebCite in the context of my discussion of the integrity of citation in a digital environment.
WebCite® is an archiving system for webreferences (cited webpages and websites), which can be used by authors, editors, and publishers of scholarly papers and books, to ensure that cited webmaterial will remain available to readers in the future. If cited webreferences in journal articles, books etc. are not archived, future readers may encounter a "404 File Not Found" error when clicking on a cited URL. [WebCite]