Nightwatch can help you check your website's condition through the Site Audit feature, and that includes letting you know the specific pages of your website that are throwing certain response codes, such as 404 and 403 errors. This allows you to remedy these response codes immediately before it affects your website’s performance online.
Here’s how you can start checking the 404 and 403 errors on your website:
Click into your preferred website’s dashboard.
Click “All pages” at the left sidebar under “Site audit.”
Click “Audit checks” at the top navigation of this page.
Filter with response code >= 403