Have you set your site's width and alignment properly in the heatmap guide?

Notes about liquid/dynamic widths

One extraordinarily common problem we see is people choosing liquid/dynamic for their width and alignment, when the site is actually fixed width. Do NOT specify this option unless you know with 100% certainty your site is truly dynamic width all the way around.

If your site is fluid but has a max or min width, data will also be somewhat inaccurate for people with very large or small browser windows. We will likely add support for this in the future.

Last, if your site has a "responsive" design, data will not be accurate at all. In the future, we may add an option to specify the pixel thresholds that your site changes design so we can segment out the proper clicks for each layout.