Application_Error, customErrors mode on, try catch ... dont want to bubble up

Hi,
I have the following settings.
Asp.net 2.0 / Vs.net 2005 / Web.config -> customErrors mode="on"
<customErrors mode="On" defaultRedirect="~/ErrorPages/Default.aspx">       <error statusCode="404" redirect="~/ErrorPages/PageNotFound.aspx"/>     </customErrors><customErrors mode="On" defaultRedirect="~/ErrorPages/Default.aspx"> <error statusCode="404" redirect="~/ErrorPages/PageNotF ...