ElDiabloConCaca
U.S.D.A. Prime
Whether or not your IP address (your internet IP address, that is) changes is based upon what kind of internet service you have. It's possible to have either a static or a dynamic IP with Cable or DSL, while with a T-1, there is a very high chance your IP is static.
Whether you need to update your IP address with DynDNS or not depends on whether your internet IP address is static or dynamic. If you don't know this information, you'll need to contact your ISP.
You will also need to ensure that your web server computer has a static IP address as well. You port forwarded port 80 to some IP address on your router -- if your web server's IP address changes (like after a shutdown or a reboot, potentially), then you'll need to go back into the router and change this IP address.
Whether you need to update your IP address with DynDNS or not depends on whether your internet IP address is static or dynamic. If you don't know this information, you'll need to contact your ISP.
You will also need to ensure that your web server computer has a static IP address as well. You port forwarded port 80 to some IP address on your router -- if your web server's IP address changes (like after a shutdown or a reboot, potentially), then you'll need to go back into the router and change this IP address.