People scan first and read second
Online reading is mostly not reading. Eye-tracking studies published by the Nielsen Norman Group described the F-shaped pattern: a horizontal sweep across the top of the text, a shorter second sweep, then a vertical scan down the left edge. It is worth being precise about what that finding means. The F-pattern is not a layout to design for; it is what readers fall back on when a page offers nothing better — no meaningful subheadings, no front-loaded sentences, no visible structure.
The same body of research identified more productive patterns. In the layer-cake pattern, readers move from heading to heading and dip into the body only where a heading earns it. That behaviour is the writer's opportunity: if every subheading carries a complete idea, a reader who reads nothing else still leaves with the argument.
Chunking and the limits of working memory
Working memory holds only a handful of items at once. George Miller's "magical number seven" was later revised downwards by researchers such as Nelson Cowan, who argued for around four chunks. The practical consequence is not a rule about list length but a discipline: group related information, give each group a label, and never ask a reader to hold three conditions in mind while they wait for the verb.
The inverted pyramid
Journalism solved the scanning problem long before the web. The inverted pyramid places the conclusion first, then the supporting detail, then the background. On a landing page that means the outcome and its qualifying condition belong in the opening line, not in the fourth paragraph. Readers who stop early — and most do — should still have understood the offer.