Handle Page not Found in Dot net 404 with webconfig

<configuration>
    <system.web>
      <compilation debug="false" strict="false" explicit="true" targetFramework="4.5" />
      <httpRuntime targetFramework="4.5" />
         
    <customErrors mode="On" defaultRedirect="~/page_not_found.aspx" >
   
    </customErrors>
     
    </system.web>
  <system.webServer>
    <httpErrors errorMode="Custom">
      <remove statusCode="404"/>
      <error statusCode="404" path="/page_not_found.aspx" responseMode="ExecuteURL"/>
    </httpErrors>
  </system.webServer>
<appSettings>
    <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
  </appSettings>

</configuration>