Clear DNS Cache (ipconfig /flushdns) (do it on the server and each client...start with the server).
The question is do you think doing this will impact IIS?
I'm just concerned about the availability of one of my webistes.
No, it's just the local client's or server's cache. Name/HostName resolution starts in the local cache...both DNS and NETBIOS for windows clients. They look here for records, and if the record exists in the local cache that overrides even the local hosts file (name resolution ends as soon as it gets a query answered).
Are you running IIS internally and/or hosting public DNS services?
Your DNS server will have DNS host and possible alias (CNAME) records for your IIS website. Don't get rid of those (though they are easy to replace). You can also clear the DNS cache on your DNS server (right click on the server...the option is there)...this does not affect your zones.
The beauty of a DNS server is that for whatever queries it does, it will cache all the answers for those
DNS resolutions works this way:
1) Check Local DNS Cache
2) Check HOSTS file
3) Query DNS Servers configured (network connections).
Any of the above fail and/or the DNS server can't respond to the query then it does the following:
1) Looks in it's own DNS Cache, and/or
2) Looks in Zone (be it Primary, Secondary, Stub) information
3) Pass the query to configured Forwarders
4) Look up Root Hints.
If item 3 fails, the DNS server will look up it's own Root Hints entries to find the Top Level/Root servers (.com...etc) that will point back to the Name Server for that Namespace. IE... microsoft.com - the Root Hints will contact the server configured for "m" and .com and find out the Name Server for microsoft.com. The query then gets passed to that server and the server should respond. www is the Host or A record for microsoft.com (or the server that is running the services) and only gets looked up after microsoft.com is established.
If Forwarding or Root Hints fail, or the Name Server can't be contact then the query will fail.
Something to consider when you are troubleshooting problems. Everything to deal with Active Directory and troubleshooting usually deals primarily with Time (Kerberos authentication) or DNS (name resolution).