http://www.my-debugbar.com/wiki/IETester/HomePage

Apart from the main function, it also provide DebugBar and Companion.JS for web development purpose.

DebugBar features
The toolbar :

• Menu to customize the DebugBar and check updates.
• Toggle the Development bar
• Alert on javascript errors
• Send page screenshot by email
• Color picker
• Resize IE window
• Zoom page
• View source code
• View MSHTML integrated ActiveX source code

The Development bar :

• View HTML DOM Tree
• View original ad interpreted source code
• View tab attributes
• Edit tab attributes
• View HTTP and HTTPS headers
• View page cookies
• Validate html code for main page and frames/iframes
• List all javascript functions
• View javascript function code
• Execute javascript code in the currently loaded page
• Get information about currently loaded page

DebugBar is free for personal use.
Companion JS

• Detailled javascript error reporting (call stack and real file name where the error occured).
• “Firebug”-like Console API feature.
• Javascript console feature useful to inspect javascript objects at runtime.
• A toolbar icon to open the Companion.JS panel.