Pin colors represent current behavior judged against a historical model of typical performance. In the case of articles, the way that we actually track and model that performance changed significantly with this new update. The old methodology identified links using their x,y coordinates on the page, which can be affected by responsive layouts and dynamic content that loads outside the bounds of the window like slideshows and carousels. In the new methodology, we use the page’s HTML structure to find links and build models for them.
However, for some sites, the HTML structure changes frequently enough such that we can’t find historical models to benchmark against our current set of positions. Possible causes include dynamic ad placement, personalization, and frequent HTML template redesigns.