After tag
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="4500000" />
</requestFiltering>
</security>
add the following tag
<httpErrors errorMode="Custom" existingResponse="Replace">
<remove statusCode="404" subStatusCode="13" />
<error statusCode="404" subStatusCode="13" prefixLanguageFilePath="" path="http://localhost/ErrorPage.aspx" responseMode="Redirect" />
</httpErrors>
you can add the Url to the error page...