> but can it be possible that 172.16.25.76 ip address could not create host entry in dns ,
Sure, requires a little change in the Registry to properly prevent it registering that address. See the article below, under "Forward and reverse per adaptor":
http://support.microsoft.com/kb/246804> or IS it possible that when user type
http://webserver , it will not points to another site it will point
> its original site, any settings in IIS ?
That could be done if you used Host Headers and the site was bound to both adapters. Are you familiar with Host Headers?
Chris