Microsoft JScript runtime error: 'Sys' is undefined
"Microsoft JScript runtime error: 'Sys' is undefined" is one of the common error we get when your web.config is not configured properly.
To resolve this issue, we need to have below lines under <system.web> tag.
<httpHandlers>
<remove verb="*"
path="*.asmx"/>
<add verb="*" path="*.asmx"
validate="false"
type="System.Web.Script.Services.ScriptHandlerFactory,
System.Web.Extensions, Version=1.0.61025.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35"/>
<add
verb="*" path="*_AppService.axd" validate="false"
type="System.Web.Script.Services.ScriptHandlerFactory,
System.Web.Extensions, Version=1.0.61025.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35"/>
<add
verb="GET,HEAD" path="ScriptResource.axd"
type="System.Web.Handlers.ScriptResourceHandler,
System.Web.Extensions, Version=1.0.61025.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35" validate="false"/>
</httpHandlers>
<httpModules>
<add
name="ScriptModule" type="System.Web.Handlers.ScriptModule,
System.Web.Extensions, Version=1.0.61025.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35"/>
</httpModules>
If you are getting this error after modifying thw web.config also then you have a another solution in below link,
http://encosia.com/2007/08/16/updated-your-webconfig-but-sys-is-still-undefined/