From a reader on (my super frick’n awesome) google ranking:

Jonah,
Without sounding too geekish here (a point sometimes lost in Corner discussions on Star Trek, et al.), there is no way technologically for Google to track your browser’s home page, your browser’s history list or where you browse apart from their site. There are a few ways to track what site you actually click on to leave their site, but these methods are far from transparent, and they don’t appear to use them. Google is what Google is because of its knack for using a variety of things to rank sites in importance in a similar way to how the human mind does. While their exact algorithms for ranking sites are closely guarded secrets (as are all search engine ranking methods), experimentation can reveal some of their methodology.
It has a lot to do with how many sites link to your particular site, and how many other sites link to those sites. This gives them a relative idea of popularity of your site, or how many people who have sites thought your site was important enough to link to. There’s much more to it, but you can see how many sites in their index link to your site by doing an advanced search. There’s a distinct correlation between number of pages linking to your page and where you are in the ranking compared to other results for the same keywords. That’s one of the reasons Google is so good, because it partly relies on the importance other people assign to your site.
OK, I’m a geek. I couldn’t even keep from sounding that way for two paragraphs. You’re probably not even taking any more applications for “web-geek guy.”