Firefox Developer Tools - Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.
myCompiler - Run your favourite programming languages online
Google Chrome Developer Tools - Get started with Google Chrome's built-in web developer tools.
CodeChef IDE - CodeChef IDE is a free online tool for developers helping them in writing codes and programs.
TrueMetrics Analytics Inspector - Analytics Inspector provides an easy way to validate web analytics and marketing integration, as well as offers a great way to quickly validate the instrumentation via the unique and simplified user interface.
Online Python - Online Python is a web application where you write codes in python language in the dedicated text space and the shell output is delivered to you in another text box on the right.