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
aXe : Automated tool to find Accessibility defects on your web site by using the aXe Chrome extension. Drop the aXe on your accessibility defects! We believ...
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...
Screenfly : Test Your Website at Different Screen Resolutions
Pa11y : Monitor the accessibility of your websites with pa11y-dashboard, and protect against accessibility errors creeping into your codebase.
The mobiReady testing tool evaluates mobile-readiness using industry best practices & standards.