What the standard says
When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined.
Why it matters
CSS can put things anywhere. A screen reader and a keyboard follow the DOM, so a visually sensible page can be nonsense in source order.
What a failure looks like
- failsA sidebar that renders first in the DOM and is read before the article.
- failsCSS grid or flexbox `order` used to rearrange content visually.
- failsA modal appended to the end of the body but shown over the middle of the page.
How to fix it
- doWrite the DOM in reading order, then position with CSS — not the other way round.
- doReserve `order` and `row-reverse` for cases where the meaning does not depend on sequence.
How A11ySignal checks it
manual
No automated rule can judge this criterion, and we will not pretend otherwise. A clean scan does not mean 1.3.2 passes — it means nothing we can measure fails. This one needs a person.
What a tool cannot tell you
A scanner cannot know what order you intended. Read the page with CSS off.