Hi!

I need some help on how to fix this Visualforce Error Message. I want to display the Open Activities and Activity History related list for a Custom Object. In its standard page, by default, this two related list is displayed but when I try to override the view page with a custom visualforce page only the custom child object related list shows.

Here's my code:

<apex:page StandardController="Object__c" extensions="ObjectExtension" showHeader="true" sidebar="true" >

    <apex:detail />    

    <apex:relatedList list="Object_Child__r"/>

    <apex:relatedList list="OpenActivities" />
    <apex:relatedList list="ActivityHistories"/>

</apex:page>

Is it something about salesforce restrictions? Like, Open Activities and Activity History were standard objects and cannot be a child of a custom object? Is there anyway I can do this right? I really need help T.T

Thanks!

Best Regards,

Pat