SharePoint 2013 How to hide main Content Place holder
Open Master page. Search for "contentBox".
Add style="visibility: hidden" to <div id="contentBox"
Final Code:
<div id="contentBox"
aria-live="polite" aria-relevant="all" style="visibility: hidden">
<div id="notificationArea" class="ms-notif-box"></div>
<SharePoint:AjaxDelta id="DeltaPageStatusBar" BlockElement="true" runat="server">
<div id="pageStatusBar"></div>
</SharePoint:AjaxDelta>
<SharePoint:AjaxDelta id="DeltaPlaceHolderMain" BlockElement="true" IsMainContent="true" runat="server">
<a id="mainContent" name="mainContent" tabindex="-1"></a>
<asp:ContentPlaceHolder ID="PlaceHolderMain" runat="server" />
</SharePoint:AjaxDelta>
</div>
aria-live="polite" aria-relevant="all" style="visibility: hidden">
<div id="notificationArea" class="ms-notif-box"></div>
<SharePoint:AjaxDelta id="DeltaPageStatusBar" BlockElement="true" runat="server">
<div id="pageStatusBar"></div>
</SharePoint:AjaxDelta>
<SharePoint:AjaxDelta id="DeltaPlaceHolderMain" BlockElement="true" IsMainContent="true" runat="server">
<a id="mainContent" name="mainContent" tabindex="-1"></a>
<asp:ContentPlaceHolder ID="PlaceHolderMain" runat="server" />
</SharePoint:AjaxDelta>
</div>
