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
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...
Skipfish : Skipfish is an active web application security reconnaissance tool. It prepares an interactive sitemap for the targeted site by carrying out a recursi...
boomerang : boomerang is a piece of javascript that you add to your web pages, where it measures the performance of your website from your end user's point of vie...
mobiReady : The mobiReady testing tool evaluates mobile-readiness using industry best practices & standards.
Monitor the accessibility of your websites with pa11y-dashboard, and protect against accessibility errors creeping into your codebase.