Do not reorder navigation links between pages
Your menu carries the same links on every page and not in the same order, so the third item on one page is the fifth on the next. W3C publishes that pattern as F66, and F66 is a failure technique, which means matching it gives you a defect to fix rather than a method to adopt. Adding an item on one page or dropping it on another is fine. What breaks the rule is shuffling the ones that repeat, and only when your site did the shuffling. A menu the user rearranged themselves is theirs to arrange.
How we find it in an audit
Scanners almost never compare one page's navigation against another's, so this is human work with a script for company. Our reviewers take a sample of templates, list the repeated links in the order they appear, and lay those lists side by side. Items that come and go between pages get ignored, because the test only asks about the links that show up everywhere. Each finding names the pages involved and the links that traded places.
How affected users experience it
Anyone who navigates by memory takes this hit, and that means screen-reader users and people with cognitive disabilities alike. The route to Help was down-arrow three times, every time, until it was not. Now the same keystrokes land somewhere else and nothing announced the move, so the map has to be rebuilt on every page. That is a lot of work to ask for something the site could have held still.
Passes vs. fails
Passes
<!-- every page, one order -->
<nav><a href="/">Home</a> <a href="/shop">Shop</a> <a href="/help">Help</a></nav>Fails
<!-- home.html -->
<nav><a href="/">Home</a> <a href="/shop">Shop</a> <a href="/help">Help</a></nav>
<!-- shop.html -->
<nav><a href="/shop">Shop</a> <a href="/">Home</a> <a href="/help">Help</a></nav>The other techniques filed under this rule
4 guides on this site are filed under 3.2.3 Consistent Navigation. W3C documents this one as a failure of that rule, so it describes a way the rule gets broken rather than a way to pass it.
This guide is our interpretation of W3C technique F66: Failure of Success Criterion 3.2.3 due to presenting navigation links in a different relative order on different pages. 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.