It seems that squid proxy somehow remembers the 403 Forbidden response and remembers it even if you reload the page which is already accessible.
Steps to reproduce:
- Put some restriction to .htaccess (like
deny from all). Open in browser, connected via squid proxy, error 403 appears. - Remove the restriction from .htaccess.
- Reload the page – the error 403 is still present!
Look at negative_ttl parameter.