I have tried many ways but unable to do this. I have set the web.config as below.
<?xml version="1.0"?>
<configuration>
<system.webServer>
<asp scriptErrorSentToBrowser="true"/>
<httpErrors>
<remove statusCode="404" subStatusCode="-1" />
<error statusCode="404" prefixLanguageFilePath="" path="/index.asp" responseMode="ExecuteURL" />
</httpErrors>
</system.webServer>
<system.web>
<customErrors mode="On" defaultRedirect="index.asp">
</customErrors>
<compilation debug="false"/>
</system.web>
</configuration>
When I try this url
http://www.aboutmanchester.co.uk/wddwd.asp
It show a message not the error page I mention but when I try
http://www.aboutmanchester.co.uk/wddwd.aspx
I goes to the custom error page.