The outer court blog has a great click survey worth checking out. Here's how it works: the site provides several screens of simple geometric shapes and asks you click on the page. At the end of the survey, the site shows you where others have clicked by superimposing dots on the image; the density of the dots providing a natural 2D histogram. Clever!
Why is this interesting, besides just being cool?
People got somewhat bent out of shape trying to intrepret the meaning of the so called "golden triangle" in Eyetools' excellent eyetracking study. Yes, many people look in the top upper left of SERPs (but there's considerable spread). Yes, it's critically important to have presence in both top paid and unpaid listings.
But the "golden triangle" isn't an a hard-wired aspect of the human visual cortex, or an intrinsic component of web technology. The triangle is the result of people looking top-left, where they've learned the engines place the most relevant content, because the engines have tested to find people look there, so the engines place their most relevant content there, so searchers look there more often, etc, in a postive feedback loop of web convention.
Some pages give users strong clues as where to click to continue. Consider, for example, the well-designed netflix new visitor home page, where -- if you've cleared cookies or are not a member -- your eye goes straight to the red "Start Now" button, or the Google classic homepage, where the eye lands right on the search box.
When you design web pages, people will look (and click) in common areas: left nav, top, etc. They do so because they've learned that's where they are most likely to find the button or link that they need.
But as the outer court's click postion tracking survey shows, where people click is also strongly influenced by page design. Follow conventions, yes, but also realize the significant role page design plays in user navigation.