Sites often behave differently in IE than in other web browsers, so having debugging tools for this platform is important.
The Developer Toolbar primarily provides a view of the DOM tree for a web page. Elements can be located visually, and modified on the fly with new CSS rules. It also provides other miscellaneous development aids, such as a ruler for measuring page elements:
http://www.microsoft.com/downloads/details.aspx?FamilyID=e59c3964-672d-4511-bb3e-2d5e1db91038
Microsoft's Visual Studio package can be used to inspect and debug JavaScript code:
http://msdn.microsoft.com/vstudio/express/vwd/
To run the debugger interactively in the free version (Visual Web Developer Express), follow the process outlined here:
http://www.berniecode.com/blog/2007/03/08/how-to-debug-javascript-with-visual-web-developer-express/
Memory leaks in JavaScript code can cause performance and stability issues for Internet Explorer. Drip helps to detect and isolate these memory issues:
http://Sourceforge.net/projects/ieleak/
To learn more about a common cause of Internet Explorer memory leaks, see Appendix C, JavaScript Closures.