What does it mean if there is a 'Cache' option on the drop-down button beside a link, but it leads to a 404 page? And how does one go about fixing this?

404. That�s an error.
The requested URL was not found on this server. That�s all we know.

^ That's the message I see, with a sketch of a broken robot beside it.

Sorry if I'm just being clueless. x)