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Deprecated HTML Tag on Page

Tags like <font>, <center>, <marquee>, <big> are removed from HTML5.

notice Impact: low DEPRECATED_HTML_TAG_PRESENT 2 min read Updated

Why it matters

Tags like <font>, <center>, <marquee>, <big> are removed from HTML5. Browsers still render some of them, but they are not maintained and signal a very old template.

Address when convenient — notices usually mark a polish opportunity rather than a defect. Estimated SEO impact: low — small marginal improvement, but cheap to fix.

How to fix

  • Replace with modern HTML + CSS equivalents
  • Example: <font color="red"> → CSS style="color:red"
  • Run the page through the W3C validator

Common causes

If the rule is firing across many pages, the root cause is almost always one of these:

  • Mixed-content sub-resources from before HTTPS migration that escaped the rewrite.
  • CDN or upstream proxy strips a security header that was set at the origin.
  • Legacy redirects send HTTPS traffic through HTTP first.
  • Test/staging hostnames leak into production HTML via hard-coded URLs.

Anti-patterns to avoid

Even with the best intentions, these "fixes" make the issue worse — recognise them so you don't ship them:

  • Mixed HTTP/HTTPS resources after migration.
  • Self-signed or expired certificates on production.
  • Long-lived secrets in client-rendered HTML or JS bundles.

How atlookup detects this

Our crawler renders each page with a real headless browser, then inspects HTTPS state, response headers, mixed content, and certificate validity. Pages where the rule fires for deprecated html tag on page are flagged on the report.

If you'd like to see this rule fire on your own site, run a free 60-second audit — every page is reported with the exact lines that triggered it.

Tools to verify the fix

Once you've applied the fix, double-check with these external validators:

Frequently asked questions

Why does Deprecated HTML Tag on Page matter for SEO?

Tags like <font>, <center>, <marquee>, <big> are removed from HTML5. Browsers still render some of them, but they are not maintained and signal a very old template.

How do I fix deprecated html tag on page?

Replace with modern HTML + CSS equivalents Example: <font color="red"> → CSS style="color:red" Run the page through the W3C validator

Is this a critical SEO issue?

Address when convenient — notices usually mark a polish opportunity rather than a defect. Estimated SEO impact: low — small marginal improvement, but cheap to fix.

How does atlookup detect deprecated html tag on page?

Our crawler renders each page with a real headless browser, then inspects HTTPS state, response headers, mixed content, and certificate validity. Pages where the rule fires for deprecated html tag on page are flagged on the report.

How long does it take to fix?

5–15 minutes per page. Most teams batch similar issues across templates so the per-page time goes down at scale.

FRAME_TAG_PRESENT

Deprecated frame/frameset Tag Present

<frame> and <frameset> are removed from HTML5 — not supported in modern browsers, bad for SEO, and catastrophic for accessibility.

FLASH_OBJECT_PRESENT

Flash Object on Page

Adobe Flash has been end-of-life since December 2020 — no browser runs it.

FORM_INSECURE_ACTION

Form Action Uses HTTP on HTTPS Page

A form that POSTs to an HTTP endpoint on an HTTPS page sends user data in the clear — a serious security and privacy failure.

MIXED_CONTENT_IFRAME

Mixed Content: HTTP iframe on HTTPS Page

HTTP iframes on HTTPS pages are blocked by modern browsers entirely — the embedded content simply does not render, breaking the user experience.