Can a spammy website affect the ranking of other sites hosted on the same server?

Matt's answer:

Matt Cutts: Today’s question comes from Remiz Rahnas in Kerala, India. [reads question] Remiz asks, “My SEO client is using shared hosting for one of their websites. When I checked other sites hosted on their server, found some spamy websites. Will that affect ranking of my client’s website?” Great question. On the list of things that I worry about, I, that would not be near the top. So, I understand and, and Google understands that shared web hosting happens. You can’t really control or help who else is on that IP address or Class C subnet. The other thing is if you were to take action just on that Class C subnet or IP address, the spammers are pretty savvy and the spammers would often migrate and go to a new IP address. So, typically, it’s not the most scalable way to tackle things. Now, I would say that, and I have seen this happen at least once, where if you have, say, thousands and thousands and thousands of spammy websites– we saw one that had 26,000 spammy porn websites all on one IP address and then one normal website– that can look a little bit bad because it definitely invites more scrutiny. You sort of say, “Well, what does this one website have to do with these thousands and thousands of spammy porn sites?” But, if you have just the normal mix that happens with any other set of shared hosting, I really wouldn’t worry about it that much.

by Matt Cutts - Google's Head of Search Quality Team

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