404-page-generator

404-page-generator is a skill for Claude Code, Codex from T4wroot/agentic-seo. It costs 82 tokens per session (676 once invoked), scanned A, a copy of 404-page-generator, MIT.

A guide for designing a 404 page, the page visitors see when a requested web address cannot be found.

In plain words
What is it for?
Use it to plan an error message, navigation, search, links to useful pages, and other ways to continue browsing.
Why use it?
It helps visitors recover from broken or outdated links instead of leaving the site.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to plan an error message, navigation, search, links to useful pages, and other ways to continue browsing.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/t4wroot/agentic-seo/404
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add T4wroot/agentic-seo --skill 404
Clone the repo
git clone --depth 1 https://github.com/T4wroot/agentic-seo

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for 404-page-generator

README.md
[![agentmods](https://agentmods.dev/badge/skills/t4wroot/agentic-seo/404/github.svg)](https://agentmods.dev/skills/t4wroot/agentic-seo/404)
Your own site
<a href="https://agentmods.dev/skills/t4wroot/agentic-seo/404"><img src="https://agentmods.dev/badge/skills/t4wroot/agentic-seo/404/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for 404-page-generator

Your own site · 80×15
<a href="https://agentmods.dev/skills/t4wroot/agentic-seo/404"><img src="https://agentmods.dev/badge/skills/t4wroot/agentic-seo/404.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 82 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 676 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00082 $0.00676
Opus 5 $0.00041 $0.00338
Sonnet 5 $0.00016 $0.00135
Haiku 4.5 $0.00008 $0.00068

Measured 6d ago against content hash cde007e2e506, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

404-page-generator scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to 404-page-generator — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/pages/utility/404/SKILL.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pages: 404 Error Page

Guides 404 error page design for UX, conversion recovery, and brand consistency.

When invoking: On first use, if helpful, open with 1-2 sentences on what this skill covers and why it matters, then provide the main output. On subsequent use or when the user asks to skip, go directly to the main output.

Initial Assessment

Check for project context first: If .claude/project-context.md or .cursor/project-context.md exists, read it for brand voice, key pages, and Section 12 (Visual Identity).

Identify:

  1. Site structure: Key pages to link (homepage, popular pages, search)
  2. Brand tone: Friendly, professional, playful
  3. Conversion goal: Recover lost visitors, drive to key pages

Best Practices

Clear Error Messaging

  • User-friendly: Neutral message explaining the page wasn't found
  • Optional 404 display: Can show "404" but avoid blaming the user
  • Empathetic tone: Acknowledge the error gracefully; turn frustration into opportunity

Navigation and Redirection

Element Purpose
Site navigation Header/footer so users know they're still on your site
Search Help users find what they need
Popular pages Links to homepage, features, pricing, blog
Similar URLs Suggest corrections for common typos
Avoid auto-redirect Unless confident of user intent

Design and Branding

  • Consistent design: Same header, footer, colors as rest of site (brand-visual-generator)
  • Avoid confusion: Users should not think they've left your domain
  • Mobile responsive: Test on all devices

Conversion Opportunities

404 pages can drive conversions by:

  • Showcasing popular products or features
  • Featuring testimonials or social proof
  • Offering special promotions or value
  • Linking to mobile app or newsletter

Technical

  • Track 404s: Monitor broken links, fix or redirect
  • Accessibility: Maintain WCAG standards
  • HTTP status: Ensure proper 404 response code

Read the full file on GitHub · 74 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 74 lines · 82 tokens per session scan A cde007e2e506

Subscribe to this mod's changes

404-page-generator is a skill published in the GitHub repository T4wroot/agentic-seo (15 stars, last pushed 7d ago), licensed MIT. It adds 82 tokens to every session and 676 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to 404-page-generator, differing in 0 lines, and is treated as a copy.

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