Sometimes, rather than serving a proper 404 error, sites will replace deleted pages with a 302 or similar redirection to some "helpful" error message.
It would be really nice, in this situation, to be able to click the Wayback Machine button and view the archived version of the original URL - i.e., the URL that I actually typed into the URL bar, the URL that I bookmarked, or the target of the link that I clicked on.
That would be nice to add (and probably easy, too), if only I would know of a way to get the original page before the most recent 3xx redirection in Javascript. :)
Sometimes, rather than serving a proper 404 error, sites will replace deleted pages with a 302 or similar redirection to some "helpful" error message.
It would be really nice, in this situation, to be able to click the Wayback Machine button and view the archived version of the original URL - i.e., the URL that I actually typed into the URL bar, the URL that I bookmarked, or the target of the link that I clicked on.