You can access it via the IP address, but a domain name makes it easier for the customer out there.
Your problem will be that normally your IP address allocated on a dialup is dynamic (Server DHCP allocated) and will theoretically never be the same between dialups, this will make it virtually impossible for someone to find your site out there again.
To register a domain you will need to have a static IP, and unless you can arrange something with your ISP you are basically screwed. But I believe there is some software out there which will link a dynamic IP to your domain name, you will have to do some "surfing" at Tucows etc. IBM Certified Specialist - MQSeries