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Custom 404 Page Checker

Reviews site markup to confirm missing pages show a helpful custom 404 with a real 404 status

Source Download skill
Repository
thedaviddias/Front-End-Checklist
Stars
74,632
Licence
MIT
Files
2 files

What it does

This skill teaches an AI agent to check a website's error handling for missing pages. When you ask it to review templates or rendered HTML, it looks for a custom 404 page with search, navigation and links to popular content, and confirms the server returns a real HTTP 404 status rather than a 200 status, which search engines treat as a soft 404. It then reports exact elements or routes that break the rule and suggests fixes.

Great for

  • Front-end developers reviewing a site's templates before launch
  • QA testers checking that broken links lead to a helpful page
  • Teams auditing SEO issues caused by soft 404 pages

Skip it if

  • Building a 404 page from scratch with design work, since the skill focuses on review and checklist guidance rather than generating full designs (the reference file is short and framework details are only summarised)
  • Sites whose server behaviour cannot be inspected, because the status-code check needs access to the rendered routes

Try asking

  • “Review my Next.js templates for whether the 404 page returns a real 404 status”
  • “Check our rendered HTML for a custom 404 page with search and navigation links”
  • “Audit this site for soft 404 problems and list the routes that return 200 for missing pages”
Step-by-step guide: how to use Custom 404 Page CheckerInstall, first run, examples, tips and FAQs

Install in 3 steps

  1. 1

    Download the skill

    The ZIP contains the 2 original files, the MIT licence and an attribution note.

    404-page.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip 404-page.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip 404-page.zip -d .claude/skills/

    Claude apps (web/desktop): Settings → Capabilities → Skills → Upload skill, and choose the ZIP.

  3. 3

    Ask for the task

    No special command needed — the agent reads the skill's description and loads it when your request matches. Try one of the prompts above.

Get better results

  • Give the agent the template files or a URL list so it can check the actual status codes, not only the source.
  • Ask for exact file paths and elements in the report so fixes are easy to apply.
  • Pair the review with a live request to a non-existent URL to confirm the 404 status.

What's inside

  • references/rule.md
  • SKILL.md

Redistributed unmodified from thedaviddias/Front-End-Checklist under the MIT licence. The assessment was drafted with AI from the skill's files on 2026-10-29. Skills can instruct your agent to run code — read SKILL.md and any scripts before installing.