The definitive heatmap: Click heatmaps are generally commercial and very expensive. Here’s a free one using Ruby. I’d be very interested to hear how this works.
It looks like it has the somewhat huge limitation of not working on sites that are center-aligned. I can see how that would be a problem.
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Don't worry, it works on center-aligned sites. The first version didn't, but now it finds the position of the very first element inside BODY and takes that as the coordinates origin. Thank you for your interest!