4XX Errors are HTTP response status codes returned by a server in response to a client request. It basically means that the request contains bad syntax or cannot be fulfilled. In other words, these errors typically occur when a URL has restricted access or rights, or simply doesn't exist.
How to verify 4XX Errors
If you're unsure whether our site auditor is reporting correctly, you can easily verify the status of your URL at https://httpstatus.io.
To do this, navigate to the SEO --> Site Auditor dashboard module. Click "4XX Errors" to see more information about which URLs have been flagged with this issue.
The dashboard will show you a list of URLs for which the site auditor has found 4XX errors.
Link Origin Page: This is the page where the link was found
Link URL: This is the URL of the page that returned a 4xx error
Link Text: This is the text of the hyperlink
If you want to verify that this is correct, open a new tab on your browser and go to https://httpstatus.io, then paste the Link URL you've copied to your clipboard. If this page confirms a 400 error, then we're reporting it correctly at our end.
What are the most common 4XX Errors?
Some of the most common 4XX errors that our site auditor will report are:
401 Error: Authorization required
403 Error: Forbidden to access the page
404 Error: Page does not exist
408 Error: Request timeout