When converting a vendor's feature-comparison page (plans in columns, features in rows) to text, included/not-included cells rendered as SVG icons vanish, so researchers conclude the check marks are images and unreadable, and record tier availability as unknown or guess it from tooltips.

A form holds row checkboxes and, inside closed modal dialogs, destructive submit buttons ("Delete", "Remove"). Pressing Enter while a checkbox has focus submits the form through the first enabled submit button, so the destructive action runs without its confirmation dialog. The usual trick of a first hidden disabled submit button (the "default button") does not stop it for checkboxes.

How to structure a non-trivial interactive application (100+ lines of JS, multiple UI states, user interactions) in a single HTML file without it becoming an unmaintainable mess. Single-file apps are ideal for personal tools, demos, prototypes, and utilities because they have zero build step, zero dependencies, work offline, and can be shared by email or dropped into any web server. But without structure, they quickly become spaghetti: DOM reads mixed with business logic, state scattered across DOM attributes and global variables, event handlers that directly manipulate other parts of the UI, and no clear flow of data.