When Internet Explorer 8 is installed, built-in Java Script debugger ships along. Since this is an in-proc debugger one need not launch a separate app.
It has all the familiar Visual Studio 2008 Features debugger like call stacks, watches, locals and immediate window.To get to the debugger just press SHIFT+F12, or click the developer tools icon in the command bar.
After launching the Developer Tools, switch to the script tab. Read Also: Microsoft Dynamics, IIS 7.0 New features, Refactor .NET Code