Sharepoint - remove Page Title

You are trying to hide the PlaceHolderPageTitleInTitleArea ContentPlaceHolder.

This PlaceHolder does not just hold the title, but certain other things as well.

Don't hide the placeholder in the master page. Rather create yourself a new Page Layout and hide whatever you dont want to see from the following within the PlaceHolder:

<asp:Content ContentPlaceholderID="PlaceHolderPageTitleInTitleArea" runat="server">
    <SharePointWebControls:UIVersionedContent UIVersion="3" runat="server">
        <ContentTemplate>
            <SharePointWebControls:TextField runat="server" id="TitleField" FieldName="Title"/>
        </ContentTemplate>
    </SharePointWebControls:UIVersionedContent>
    <SharePointWebControls:UIVersionedContent UIVersion="4" runat="server">
        <ContentTemplate>
            <SharePointWebControls:FieldValue FieldName="Title" runat="server"/>
        </ContentTemplate>
    </SharePointWebControls:UIVersionedContent>
</asp:Content>

Or add this CSS to page

<style type="text/css">
#pageContentTitle {
display: none !important;
}
</style>

Add the below lines in page layout just above Publishing:EditModePanel tag.

 <script type="text/javascript">
  function hidePageTitle() {
     var elem = document.getElementById('pageContentTitle');
     elem.style.display = 'none';
 }

 _spBodyOnLoadFunctionNames.push("hidePageTitle"); 
 </script>