Phantomas : PhantomJS-based web performance metrics collector and monitoring tool
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.
BounCA : BounCA is a tool to manage your personal SSL certificates and authorities in a central and easy to use interfaces. It provides an easy accessible web ...
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...
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 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 common errors. Use the online scanner or the CLI to start checking your site for errors.