Internet ExplorerOpen Internet Explorer. Click on the "Tools" menu and then click on "Internet Options." Click on the "Advanced" tab. Deselect "Disable script debugging (Internet Explorer" and then deselect "Disable script debugging (Other)" in the Browsing options. Click on the "Apply" button and then click on "OK" to confirm your changes.
http://www.youtube.com/watch?v=nYkdrAPrdcwReferences:C-Point: JavaScript Tutorial: Enabling JavaScript Debugger
Blogs MSDN: Scripting Debugging In Internet Explorer
Better Explained: How To Debug Web Applications With Firefox
Getfirebug: JavaScript Debugger and Profiler : Firebug
Resources:Get Firebug: Firebug Web Development
