Hi,

Can i ask what country you live in, and whats your ISP.

I ask because i know that here in the UK some ISPs block ports specifically so that you can't run mail or web servers.

for example, ukonline say:
Is there anything else I need to know?

We do not offer a newsgroup service on our broadband services. We also block ports 25, 80, 8080 and 3128 on all of our broadband services in order to maintain quality of service for all of our customers, so you will not be able to run a mail or web server.
http://www.ukonline.net/broadband/broadband22Mb.php

Additionally you will need to have a static IP address, otherwise if you turn anything off you will loose the one you currently have and then people wont be able to reach your site, as when you turn back on you will be assigned a different one. There is also the possibilty that your IP address may change even if you do not turn anything off. In a different post here on AO, someone said that dynamic ones work as follows: (sorry to whomever said this, i can't remember the thread, or your name)

1) ISP assigns you a leese for an IP Address for X amount of time
2) Your computer/router/modem will make three attempts to keep the IP, 1 once half way through the leese, once 3/4 of the way through and once at the end. If none of these are succesful the ISP will give a new leese with a new IP address for time X
3) If any are succesful you keep the IP address and the leese is renewed for time X

Hope this helps