Does anyone know what might cause this error in IE when my page loads:

Error parsing attribute 'enableeventvalidation': Type '_Default' does
not have a public property named 'enableeventvalidation'

This is the line of code it stops on:
<%@ Page Language="C#" AutoEventWireup="true" Inherits="_Default"
Debug="true" EnableEventValidation="false" %>
Source File: /main/default.aspx    Line: 1

I am just copying my site from another server.  It works fine on the
first server.  Apparently I need to get _Default to have the above
mentioned property.  How would I do that?