When domains expire, the registrar shifts the domain's name servers to special "parked" nameservers. As soon as the domain is renewed, the name servers are switched back. However, the global registries serve 2-day time-to-live (TTL) values when delivering name server glue records.
This means that most people who haven't already seen the "parked" domain will be able to see the site after it's renewed. However, anyone who tried to access the domain while it was expired (including, most likely, you -- its registrant) may continue to see the "parked" page until the two-day time-to-live period expires. It is possible to see the exact remaining time with the Unix command line utility dig, if it is present on your local system.
Although this doesn't tend to affect most site visitors, those who are affected have no recourse unless they have direct control over their local name servers. This is standard to the global registries that operate each TLD and thus works exactly the same for all registrars. It is not something we or our registrar chose or have control over.
In order to prevent this, NearlyFreeSpeech.NET recommends that you either use our auto-renewal feature to make sure your domain never expires or pre-renew your domain so it is never within a year of expiring.