I'm trying to setup squid in front of apache, but sometimes it caches error pages like 404, 403, and if apache is too busy at a time, squid can't get a page from it, it will cache an access denied error, have to refresh lot of times to get rid of the cache, how to setup rules to have squid not to cache these kind of error pages?

i'm using squid 2.6.

thanks for help.