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...
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
Yellow Lab Tools : Online test to help speeding up heavy web pages
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...
Monitor the accessibility of your websites with pa11y-dashboard, and protect against accessibility errors creeping into your codebase.