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
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.
tota11y : an accessibility visualization toolkit that aims to reduce the friction of a11y testing
webhint : webhint is a linting tool that will help you with your site's accessibility, speed, security and more, by checking your code for best practices and co...
The mobiReady testing tool evaluates mobile-readiness using industry best practices & standards.
