netcat - Netcat is a featured networking utility which reads and writes data across network connections...

Firefox Developer Tools - Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.

Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.

Google Chrome Developer Tools - Get started with Google Chrome's built-in web developer tools.

SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.

Code Cola - Code Cola is a chrome extension to editor online pages' style visibility.