tota11y : an accessibility visualization toolkit that aims to reduce the friction of a11y testing
Diagnostic.css : Diagnostic.css is a stylesheet which allows the user to test for common errors in a page's markup.
Also : https://github.com/karlgroves/diagnostic.css
Appium : Appium is an open source test automation framework for use with native, hybrid and mobile web apps.
It drives iOS and Android apps using the WebDriver...
Maestro : Maestro is the easiest way to automate UI testing for your mobile app.
Site Valet : Web Tools for Quality, Accessibility, Standards Compliance.
The mobiReady testing tool evaluates mobile-readiness using industry best practices & standards.