With VS 2008 and IE 8, JavaScript debugging is automatically enabled even if script debugging is set to disabled in IE8 settings. This will help developers in debugging scripts without having to change debugging features within browser. While this is a good feature for most developers, it takes up to 10X time to load a page that is heavy on client side scripts.
How to disable script debugging in IE8?
Go to a Command Prompt (cmd) and Enter…
reg add HKLM\SOFTWARE\Microsoft\VisualStudio\9.0\AD7Metrics\Engine\{F200A7E7-DEA5-11D0-B854-00A0244A1DE2} /v ProgramProvider /d {4FF9DEF4-8922-4D02-9379-3FFA64D1D639} /f
To enable it again go to the Command Prompt and Enter...
reg add HKLM\SOFTWARE\Microsoft\VisualStudio\9.0\AD7Metrics\Engine\{F200A7E7-DEA5-11D0-B854-00A0244A1DE2} /v ProgramProvider /d {170EC3FC-4E80-40AB-A85A-55900C7C70DE} /f
Tip from:Gregg Miskelly of Visual Studio team debugger team