3 ideas
On the web, users move with purpose and rarely read text word-by-word; they scan for keywords, links, and visual anchors that match their goal. Content must therefore front-load conclusions, use scannable headings, and highlight meaningful words, because prose written for linear reading is mostly ignored.
Human attention degrades at predictable system-response intervals: under 0.1 second feels instantaneous, up to 1 second keeps thought uninterrupted, and beyond 10 seconds the user mentally disengages and switches tasks. Designing within these thresholds determines whether a system feels responsive or abandoned.
When most websites do something the same way, users come to expect that behavior, so deviating from established patterns forces relearning and increases errors. The mechanism is that usability comes from meeting accumulated user expectations across all sites, making conformity to convention more valuable than creative novelty in interface design.