<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>

<configuration>
    <system.web>
        <customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
    </system.web>
</configuration>

<?xml version="1.0"?>
<configuration>

  <system.web>
    <customErrors mode="Off"/>
  </system.web>

  <system.web>
    <compilation debug="true"/>
    <authentication mode="None"/>
  </system.web>
</configuration>

<system.web>
    <customErrors mode="Off"/>
    <compilation debug="true"/>
    <authentication mode="None"/>
  </system.web>
</configuration>