If a page was (re)moved and now shows '404 page/file/site not found' error, this tiny extension uploads archived version of a page (from wayback machine at archive.org). If 404 error related message is not put in the HTML title tag of the missing page, this extension will not automatically look for an archive, but user can click on Archive button instead. Clicking on that button will show archived version of any page. False detection occurs when an existing page is about this error and has error message in HTML title tag. However, these pages are not common. When this happens, just click Cancel when confirm box appears, and that page will be added to whitelist and will not be mistaken again for missing page.
||Windows XP/Vista, Firefox: 1.5 2.0.0