regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
Explorer Exposed! : These CSS bugs are all found only in Internet Explorer, versions 5 and higher. To see the demos properly, they must be viewed in IE, of course.
Charles Web Debugging Proxy : Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP and SSL / HTTPS traffic between their machine...
Deploystack : Curated list of best tools for launching your website. Find how to get the best hosting, cheapest domain, files storage, monitoring and more.
JSDB.io : JSDB is a collection of the best javascript libraries
