"Most mistakes are simply not noticed. Seotool will help you spot the stupidest mistakes."
https://vanyapr.github.io/seotool/
Seotool is a small library for checking most popular search engine optimization mistakes on the fly.
Insert the script before the closing body tag. <script src="seotool.min.js"></script>
Reload the page. Seotool will display errors at the bottom of the page.