Keep repeated components in the same order
Everything that repeats across your pages keeps the same relative order, every time. G61 is that technique, and it carries real weight, because W3C lists exactly one sufficient technique for the consistent-navigation rule and this is it. Relative is the working word. Items can be added on one page and dropped on another without breaking anything, as long as the ones that survive keep their sequence. A products section that swaps product links for training links still passes, so long as the header, the search box and the main navigation stay where they were. What breaks it is reordering, and specifically reordering your site did rather than reordering a reader asked for.
How we find it in an audit
We take a sample across every template on the site, list the repeated components in the order they appear, and lay those lists beside each other. Header, search, main navigation, footer, utility links. Items that come and go get ignored, because the test only asks about the ones that repeat. This gets decided at the template level rather than the page level, so a finding usually names a template and the change gets made once.
How affected users experience it
Predictable placement is what makes a site quick to use without sight. A screen-reader user learns that the search box comes after the logo and before the navigation, and from then on they go straight to it. Someone with a cognitive disability builds the same habit visually. When the order shifts between pages, both of them lose the shortcut and go back to reading the entire page header every time, which is slow, tiring and completely avoidable.
Passes vs. fails
Passes
Every template renders the same navigation order, and product pages simply highlight where the visitor currently is.
Fails
The main navigation reads Home, Products, Pricing, Contact, except on product pages where Pricing jumps to the front.
Other ways to satisfy this rule
4 guides on this site are filed under 3.2.3 Consistent Navigation. W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
This guide is our interpretation of W3C technique G61: Presenting repeated components in the same relative order each time they appear. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.