Tracking scroll depth is interesting, but percentage isn't all that helpful. The number of comments on a blog post will mess with the data, for example (you won't be able to reliably compare Post A to Post B).<p>What might make more sense is tracking who scrolled down to the end of the .blog-post div, to the end of the .comments div, and to the end of the footer. Or whatever makes sense for the content on your page(s).