<hr><i>anonymous added on 2010-07-19 11:29:33:</i><br>
I think it would be wiser to not ignore the sum but serve only the URL with the correct checksum if checksummed URL is requested.

If the checksum was ignored and you changed the repo which is served on a particular address (either by editing the repo or by changing some redirection) then the new style could be cached on an URL referenced from an old page which is exactly what is to be avoided.