You say you are on ATT Broadband, you have to check with them to see if they allow you to run a web server on your connection. It usually to do with the company wanting to connect the most amount of users to their servers so their stop the uploading from users on certain ports to free up their bandwidth.
I know over here in the uk, some of the cable companies who provide cable broadband do not allow you to run a server and block ports at their end. I think the web browser port is 80 and 21 for ftp so ask your isp about these ports Set the ftp server up in IIS and ask somone to see if they can connect to it also.
you can always get me on messenger if you want any further help