Quick answer
Keep heading levels in a sensible order so a section does not jump from, for example, H2 straight to H4. NOTABIS reports a skipped level when the measured heading sequence moves down more than one level; it is a low-priority structure review, not a ranking penalty. Fix the hierarchy when the jump makes the page harder to scan or understand.
What the issue means
HTML headings describe the nesting of sections. An H2 normally starts a section under the page’s H1, and an H3 starts a subsection under that H2. A skipped level looks like this:
<h1>Trail running shoes</h1>
<h2>Choosing a pair</h2>
<h4>Grip and terrain</h4>
The H4 does not say that the section is less important because it has smaller text; it says that an H3-level section is missing from the document outline. CSS can change how a heading looks, but it does not change its semantic level.
Why it matters for SEO
Logical headings help readers scan a long page and help assistive technology describe its structure. They also give search systems useful context alongside the page text, title, links, and other signals. Google does not require a perfect numerical heading sequence, and a skipped level by itself does not mean a page cannot rank. The practical concern is an accidental template hierarchy that obscures the page’s sections.
How NOTABIS detects it
The skipped-heading-level rule reads H1 through H6 elements from the measured HTML in document order. It remembers the previous heading level and flags the page if a later heading is more than one level deeper than that previous heading. The first heading is not treated as a skip, and moving back up the outline is allowed.
This is a page-level markup check. It does not judge heading wording, visual size, CSS visibility, or whether client-rendered headings appear after the initial response. Compare rendered evidence when a JavaScript application changes the heading tree.
How to check it yourself
Inspect the rendered DOM and list the heading levels from top to bottom. Then use View Source to see whether the same headings are present in the server response. Look for duplicated desktop/mobile components and headings inserted by widgets, since either can change the sequence.
How to fix it
Choose the page’s main subject as H1, use H2 for its major sections, and use H3 or deeper headings only inside the section that owns them. Change the element level in the template rather than adding empty headings to make the sequence look complete. Recheck anchor links, styling selectors, and responsive components after the change.
Corrected structure:
<h1>Trail running shoes</h1>
<h2>Choosing a pair</h2>
<h3>Grip and terrain</h3>
If a block is visually styled as a heading but is not a real section, a paragraph or other element may be more accurate than forcing it into the outline.
When this is intentional or does not need fixing
A short page may begin with an H2 because its template supplies the page title elsewhere, although the resulting experience should still be understandable. A component library can also produce a technically skipped sequence without confusing users. Review the rendered page and accessibility experience before treating a low-severity finding as urgent.
Related issues
Compare missing H1 tags and multiple H1 tags when checking a template’s complete heading structure. Empty headings are another useful template check when that guide is available.
Run a NOTABIS audit
NOTABIS lists pages whose measured heading sequence skips a level, so you can inspect the responsible template and decide whether the structure needs changing.