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.
Which loads faster? : Pages compete head-to-head in your browser to see who's fastest!
tota11y : an accessibility visualization toolkit that aims to reduce the friction of a11y testing
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.
Diagnostic.css is a stylesheet which allows the user to test for common errors in a page's markup.
