Our website went down for some people today because dotster changed their IPs for some of their nameservers. ( ns1.nameresolve.com, etc ) ..
Which made me wonder, all the people that had went to our site, would have it cached, people that have not made it to our site would look it up in their DNS, which would not have it and check the next DNS in the chain, which eventually would check nsX.nameresolve.com ( and that would fail if the record was old ).. So at which DNS does it check nsX.nameresolve.com.
Please feel free to edit my question to make it more clear.