404 Not Found" error? No worries, Mozilla add-on provides a solution by uploading the archived version of the page.
When you stumble upon a missing page that displays the dreaded '404 Page / File / Site Not Found' error message, this extension steps in and uploads an archived version of that page. The archives are pulled from the wayback machine at archive.org. However, if the missing page doesn't have the error message in its HTML title tag, the extension won't automatically look for an archive. In that case, you can click the 'Archive' button that you've customized and placed in your browser's toolbar. By clicking that button, you can quickly access an archived version of the lost page.
Occasionally, you may run into a "false detection," which happens when an existing page happens to be about the error and has the error message in its HTML title tag. But this issue is rare. If you do encounter a false detection, simply click "Cancel" when prompted by the confirmation box that appears. This way, that page will be added to a 'whitelist' and won't be mistakenly identified in the future as a missing page.
This software extension is compatible only with Firefox. Overall, if you want to save time and heartache hunting down missing webpages, this extension is worth checking out.