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...
SPOF-O-Matic : Chrome extension for detecting and simulating frontend Single Points Of Failure. Detects likely third-party single points of failure as you browse and...
Sitespeed.io : Sitespeed.io is an open source tool that helps you analyze and optimize your website speed and performance based on performance best practices. It col...
Introduction to WAI ARIA : This article is for those who are new to ARIA. You need an understanding of HTML and the potential difficulties that people with disabilities can face...
Monitor the accessibility of your websites with pa11y-dashboard, and protect against accessibility errors creeping into your codebase.