What are the F12 Developer Tools in Internet Explorer?
The Developer Tools provide built-in features to analyze applications with the JavaScript profiler, CSS Editor, and the new Network Analyzer. Building on the tools that Internet Explorer 8 provides, the Developer Tools in Internet Explorer 9 add a new tab for inspecting network traffic, improve the performance of working with large JavaScript files, and add a user-agent switching tool. They can help IT pros and developers ensure that their applications work with Internet Explorer 9.