Error ASP web.config, when run locally

Hi guys,

I need to make some changes to aspx website, so I want to run it locally.

I have loaded web site locally on IIS 7. I have done all configuration, now when I run it I get following error.
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Detailed Error Information

Module IIS Web Core
Notification Unknown
Handler Not yet determined
Error Code 0x800700b7
Config Error There is a duplicate 'system.web.extensions/scripting/scriptResourceHandler' section defined
Config File \\?\C:\inetpub\wwwroot\web.config
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Config Source

4: <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
5: <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
6: <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">

I found some solution
The workaround for the first scenario is to update the application-level Web.config file by including the boilerplate configuration text from a Web.config file that was generated automatically by Visual Studio 2008.

but I hardly understand it, what should I do, because I am quiet new to aspx.

Thank you

I don't use system.config files or IIS, but the error message sounds plain enough. Somewhere in your config settings you have defined some attribute more than once.

The line I have put in red above gives me an error, config file was already included in website, I am only doing some update to website...
I have checked file and it is not repeating anywhere, so I am still confused.

Thanks