[DotNetDevelopment] Log/QueryString in Error page

[Kris-I]

Hello,

I have this in my web.config

 <customErrors defaultRedirect="~/Errors/ErrorPage1.aspx" mode="RemoteOnly">
       <error statusCode="404" redirect="~/Errors/ErrorPage2.aspx"/>
       <error statusCode="500" redirect="~/Errors/ErrorPage1.aspx"/>
 </customErrors>

I'd like to know when I arrive in page ErrorPage1 or ErrorPage2 the cause of
this error. Then I'd like to know If I can get the HTTP_REFER on this page,
and put only on these pages debugging info.

Regards,