Welcome to the land of 'consumer' high speed without a static ip address. If I understand your question, the websites hosted on your pc aren't available. You would need to ensure the DNS on the external DNS provider has the latest ip address. Since you have a dynamic ip, a lot of services block port 80, 25. This isn't an IIS problem per se as much as a connectivity. I would do this.
1) ensure you can telnet yourIP 80 from external to your network
2) ping from an external source and see if they are up and running.
I'm not sure if 1, 2 are working externally so that is why I mentioned. For your internal machines to hit the same website. I'd check your dns settings on your machines to ensure they can resolve the same addresses. I run a Domain Controller at my house for years where the domain name was aspdot.net (which is also an external domain I own). I had to 'add' ip addresses on the DC so internal boxes knew how to resolve the 'www' domain. Hope that helps provide some direction.
Steve Schofield
Windows Server MVP - IIS
http://weblogs.asp.net/steveschofield
http://www.IISLogs.comLog archival solution
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