How does Google consider site-wide backlinks?

Matt's answer:

Today’s question comes from Chris in Poland. Chris asks, “Are sitewide backlinks considered good or bad by Google? Or do they just count as one link from the whole domain?” It’s an excellent question because– let’s tackle it from both the algorithmic standpoint and from the manual standpoint. On the algorithmic standpoint, typically, I’ve said before, if we have keywords, the first keyword counts some, the next keyword counts a little bit but not as much. The third keyword, not as much. So even if you do keyword stuff, and even if you throw a ton of keywords, at some point it becomes asymptotically diminishing returns. And it doesn’t really help you anymore. You can imagine the same sort of thing– if we see a link from a domain, we might count it once. But if we see 50 links from a domain, we still might choose to only count it once. So on an algorithmic side, we do a pretty good job of compressing those links together. But then there’s also on the manual side. So imagine that you have a Polish website, and then you see a sitewide link in English talking about rent cheap apartments. To a regular person, that looks pretty bad. So certainly it does happen that you have sitewide links, maybe have a blog roll or something like that. But if I or a manual web spam analyst were sort of doing an investigation, and we got a spam report– you’re an English site, and you’ve got a sitewide Polish link or something like that or vice versa, it looks commercial or it looks off topic, low quality, or spammy, then that can affect the assessment on whether we want to trust the outgoing links from that site. So sitewide links do happen. It’s completely natural. You might have a privacy policy, copyright policy, all that sort of stuff. But when we see sort of irrelevant or off-topic links or even spammy links sitewide, then that is the sort of thing that does make a spam fighters ears sort of perk up a little bit. I think we handle it very well on the algorithmic side, but we do manual investigations as well. Hope that helps.

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

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