A HighRankings Forum thread discusses the possibility that Google themes sites. That is, Google groups sites together because of the relevancy of the link. So, for example, if you got 300 links to your blue widget site from a bunch of humor sites, wouldn't Google think that the blue widget site is actually about humor (and not so much about blue widgets)?
If you do a Google search for related:www.mysite.com and find similar sites, wouldn't that be theming?
As Randy says, "[I]t's more than just about the words on the page. You'd also need to factor a broader range of linking relationships between multiple sites into the equation."
Ian McAnerin mentions that the related: search operator doesn't really theme sites as we'd expect. It's based on the type of backlinks received.
However, in the end, people agree that some sort of theming exists:
I think Google does actually Theme sites. This may split a site as covering a number of related themes.
The discussion spans three pages (so far) and there appears to be no end in sight. What are your thoughts on Google's "theming?" Share your thoughts at HighRankings Forum.
