if the admin  is merely to alter/change/delete the actual link  itself the this wouldn't immediately affect the actual destination of that link.

so users who are currently using the destination of that link won't be affected.

and even if it was; the actual, current html has already been downloaded to their browser for the immediate, if the alteration changes that html then they will see it on their next visit to the link, or a refresh (if it still exists).

if the question  is that the admin actually change the link exactly at the same time a user clicks the link then this can be sorted by locking the application  during the alteration ... but personally I wouldn't bother, how often is this to occur - how likely is it that admin/customer actually clash time milliseconds - and even if they did ? so what - so the user gets his web experience messed up for a few milliseconds (who cares !) - its hardly a cashpoint machine is it !