What is the most common on-page SEO mistake?

Missing or duplicated title tags are among the most common — template-generated pages often inherit a generic title or share the same one across URLs, which weakens the signal about what each page is about.

Is it bad to have two H1 tags?

It is not ideal. A page reads most clearly with one H1 stating the topic. Multiple H1s (or none) can weaken the page's clear topical signal, though search engines are generally tolerant — fix it when you can.

Do meta descriptions still matter?

They don't directly decide rankings, but a description you control usually produces a cleaner search snippet than text the engine pulls at random. A missing one is worth fixing.

What happens if I forget the canonical tag?

Without a canonical, search engines may split ranking signals across near-duplicate or parameterized URLs. Setting it tells them which version is preferred.

Can a tool catch all of these automatically?

A rule-based scanner like SEOAudit can flag each of these from the page's HTML automatically and reproducibly. It surfaces the issues; applying the fixes is still up to you, and it does not guarantee a ranking outcome.

The most common on-page SEO mistakes (and how to catch them)

Missing or duplicated title tags

The title is what shows in the search result and the browser tab. Pages shipped from a template often inherit a generic title ("Home") or, worse, share the exact same title across URLs. Either way, search engines get less signal about what the page is about.

Thin or missing meta description

A missing or one-line meta description means the search engine may pull arbitrary text into the snippet. A descriptive description you control usually produces a cleaner result. SEOAudit flags a missing meta description as a WARN so you can write one.

Multiple H1s (or none)

A page should have one clear H1 that states the topic. Builders sometimes drop an H1 entirely or stack several because each section component ships its own. Either extreme weakens the page's clear topical signal.

Images without alt text

Every meaningful image should have alt text — for accessibility (WCAG 2.2) and for image search. Carousels and icon sets are common culprits. A rule-based scan flags each missing alt.

Broken or missing canonical

A canonical tells search engines which URL is the preferred version. Forgetting it on filterable or parameterised pages can split ranking signals across near-duplicates. A missing canonical is an easy WARN to miss by eye.

Missing viewport or Open Graph

No viewport tag can hurt mobile rendering. Missing Open Graph (og:title, og:description, og:image) means shared links render as plain text instead of rich cards.

Why they slip through

These are invisible in a visual preview. A page can look perfect in the browser and still ship a missing canonical or duplicated title. That is exactly why a tag-level, named-rule check beats eyeballing.

Catching them with a rule-based scan

SEOAudit encodes these as 10 named rules and tags each PASS / WARN / FAIL, so the same page always produces the same verdicts. Re-running after a fix confirms the mistake is actually gone.

Authoritative references

Google Search Central — on-page SEO: https://developers.google.com/search/docs/crawling-indexing/on-page-seo
W3C WAI — images tutorial: https://www.w3.org/WAI/tutorials/images/
Open Graph protocol: https://ogp.me/