thx for your usefull link.
I use 5.5R2 version.
I read the blog post and used the code below in my root page(master page), but by using this code in root page, not only the page placeholder webpart but also any othe webparts not shown in subpages...
<cms:CMSContent runat="server" id="cntLeft" PagePlaceholderID="plcLeft">
<cc1:cmswebpartzone id="pageTitle" runat="server" />