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...
Pa11y : Monitor the accessibility of your websites with pa11y-dashboard, and protect against accessibility errors creeping into your codebase.
Mink : Mink is an open source acceptance test framework for web applications, written in PHP 5.3.
WebPagetest : Run a free website speed test from multiple locations around the globe using real browsers (IE and Chrome) and at real consumer connection speeds.
Type-a-file : Below you’ll find some text marked up with the core elements of Type-a-file. View the source code to find out how to use them on your own site. This e...
Diagnostic.css is a stylesheet which allows the user to test for common errors in a page's markup.