>is the IP banned or just the domain name or just the page?
Not by any means a definitive answer, but I'll give it what I know. It wouldn't be logical to ban a page, all someone would have to do is give the page another file name. I do know that an individual page can be removed from Google by request, but that's not the same as them banning it by their choice.
Google, for example, spiders by both IP number and domain name. They save the pages in the cache by IP number, not domain name. On the results page, even though they have the actual domain name listed on the results page, it's connnecting by domain name or IP number, depending on the situation.
When I cancelled a domain (my own choice), the IP number was assigned by the host to another site right away. My old pages were still visible in the cache, but when clicking on the link from the results page, it went to the other site - so it arrived there by IP number, even though the URL listed at Google was my old one, with the page title and the Google description showing. Does that make sense?
Case 2: What just happened with another site I'm familiar with (not banned) is that they just changed hosts (and IP numbers) last week. The link from the Google page is getting to the new site by domain name yet the old page is still in the cache.
In the first case, it was going to the IP number (different site and domain name) and in the second case, it is going to the site by domain name.
The difference between the two is that in the first case the domain name was cancelled and not on the net any more. With the second one, it had just moved (changed addresses) and still existed, so the domain name resolved to the new IP.
This second will undoubtedly be changed next update - so there will be a matching done between the domain name and the IP number, just as there was in the first case.
I suspect it may default to domain name, but bring up the IP number if the domain is not resolvable.
Case 3: A site that was was banned from Google (the domain name) and is moved to another server with another IP number apparently took it's history with it. That domain name is not indexed by Google after many, many months. It's the domain name that's banned.
In the case of Google, they spider both, and from what I can surmise they cross-match domains and IP numbers - so changes are reflected at the following update when there isn't a match.
Now if someone is banned and changes hosts (different IP number) if it's IP banning, the site in violation would still be listed because of the different IP number, while the new site taking the old IP number would be banned. That is not logical.
Banning by domain name is what I'd assume from these observations.
Now, in the case of shared hosting, that's a little muddy to me. I do know for certain that *ALL* sites at Hypermart with the subdomain are banned at Alta Vista. So if one is banned, they are all banned. Same with other free hosts. When using paid domain hosting there, I believe a unique IP is assigned, so a whole different situation exists.
If a domain name were banned,I'd get it fixed or get a different domain name.
In the event of IP banning, if that's how it's done, all that would need to be done is to move an offending site to another IP number and the domain would stay intact. That wouldn't make sense either.
There's got to be some matching, although I would sincerely hesitate to host where there's a possibility of sites having been banned. In fact, I was advised against using a certain host for this reason. I do believe there's historical date somehow kept on certain IPs or blocks of IPs.
IP banning itself I don't know about - I believe it's more commonly domain names, but that at times IP banning penalties can happen. I do believe that when a site at an IP is banned, all others are banned with it, but what combiniation is used I can't imagine.
I'd be interested in more info on this, too.