Step1: In web.config file Write the following code
<system.web>
<customErrors mode="On">
<error statusCode="404" redirect="PageNotFound.aspx" />
<error statusCode="403" redirect="PageNotFound.aspx" />
</customErrors>
</system.web>
<system.webServer>
<httpErrors errorMode="Custom" existingResponse="Replace">
<remove statusCode="404" />
<remove statusCode="403" />
<error statusCode="404" path="PageNotFound.aspx" responseMode="Redirect" />
<error statusCode="403" path="PageNotFound.aspx" responseMode="Redirect" />
</httpErrors>
</system.webServer>
Step2: Settings need to be updated in IIS7
1) Open IIS
2) Select your application
3) Open Error Pages under the IIS section -> clicks Open Features
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4) After clicking Open Features tab we will get below shown window. Now click Edit Feature Settings tab
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Then we will get below shown window,
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In the above window select radio button Custom Error Pages àok
_Step3:
_Open the file:
C:\Windows\System32\inetsrv\config\applicationHost.config
_And change:
<section name="httpErrors" overrideModeDefault="Deny" />
_To:
<section name="httpErrors" overrideModeDefault="Allow" />