Internet Explorer GPP vs GPO

Hi,

I am trying to config IE8 (W7), with GPO and GPP. I have trusted zone in GPO and I want to use GPP for other settings like default webpage.
I loaded the GPP and added a web site as an default web page, but I notes that it was trusted zones in GPP also and they where green.
I could not find a way to disable them, the GPO is on a OU level over the GPP. I gues GPP override the GPO...

I would like to understand how to use GPO vs GPP to set IE settings

/SaiTech