Warn about HTML Markup code accessibility issue.

First, Download the a11y.js

Second, include it before </body>

<script src="a11y.js"></script>

Third, open the console.

if you need to test your website or any website without download the file you can put this code in the console.

var script = document.createElement("script");
script.type = "text/javascript";
script.src = "https://cdn.rawgit.com/Muhnad/a11y-checker/master/a11y.js";
document.body.appendChild(script);

Thanks to @Paul Adam for upload the script in rawgit.

MIT