Can I exclude certain words from Googlebot?

Matt's answer:

We have a question from Youser. I’m doing the question mainly because I like to say: Youser. Youser asks: “Is there a way to tell Google bots to exclude recurring words on a website such as ‘leave comment’ or ‘print page’ when indexing in order to improve the keyword density?” Well, Youser — um — I in general wouldn’t worry about that. So, whenever people start talking about keyword density, they are usually worried about stuff that are more granular level than they should be worrying about. If you’re at the point where taking out the words ‘leave comment’ or ‘print page’ seriously affect the keyword density of your page, you have some pretty outrageous keyword density. In general, I wouldn’t worry about that. Now, Yahoo has an interesting standard where they have said you can block out parts of a page and it won’t index parts of that page, which I think is a pretty cool idea. Um, the problem that we’ve seen whenever we have looked at the usage of that on the web, is not that many people use it. And to implement support for that, and then maintain support for that as we write new indexing code would be a little bit prohibitive. So, Google, at least right now, doesn’t have a way to say: OK, this part of the page —  don’t index this part of the page. In theory, you could throw it in an iframe that was then blocked in text, and I can guarantee you at that point you are probably putting a lot more effort into trying to leave out that ‘leave comment’ or ‘print page’ phrase than you probably should be. So, in general, if you are at the point where you are worried about keyword density, I would take a step back, take a deep breath, think about other good content you can write and other good ways that you can promote it, rather than worried about that level of detail.

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

Original video: