, I'll almost bet it is in violation of your contract with your ISP to host a public website with a residential account.
The wording may need to be refined. The TOS more likely uses terms like "commercial website" or for "commercial purposes", Many residential accounts may run web cams, PCAnywhere, home automation servers and such, which probably are not restricted in the TOS. I know that the company I work for blocs access to servers running on ports other than the typical 80, 443, etc. I think it is due to the fact that many Trojan applications connect to servers operating on non standard ports.