This page has one or more controls that do not correspond with controls in a page

Problem

When you open a page in SharePoint designer it complains that there is a conflict and that the placeholder for the master page is missing.

Explanation

This occurs when a user modifies a master page. The master page no longer contains that objects that the derived page expects, so SharePoint Designer gives an error (note that SharePoint will still recover gracefully from this, so some users simply switch between valid and invalid master pages instead of addressing the problem directly.

Cause

User used SharePoint designer to delete or comment out a placeholder.

Resolution

Use CSS or mark the server control with the visible=false attribute to hide the placeholder in question.

<asp:ContentPlaceHolder id="PlaceHolderSearchArea" runat="server" visible="false">
<SharePoint:DelegateControl runat="server" ControlId="SmallSearchInputBox"/>
</asp:ContentPlaceHolder>