I am not a web host, but plan to in a couple of years, after college. I don't think that you should put up advertisements of any sort unless you are providing free hosting. I for one would be put off if I was trying to access a web site and got an error message that sent me to some crazy web host I've never heard of.
If this web site was of the professional kind, and not just some random link that I followed, I would definitely think less of them for having error messages that were not only not the default ones, but ones that went to some hosting company.
A Collection of Web Hosts
Small biographies on hosts, uptime reports and some reviews
Feel free to add your review or add a host that isn't on the list.