I have some confusion over MasterPageFile attribute.There are two options available for master pages, custom master page and default master settings in SharePoint Designer. One master page I have set as custom and other with default master page. Now every new page I am creating it is taking custom master page by default and also all old(pre defined) layout pages (e.g. welcomelinks.aspx) taking custom master page.
1) even I am giving MasterPageFile attribute with ~masterurl\custom.master in any layout it is taking custom master page by default the what is the exact use of MasterPafeFile=''~masterurl\custom.master" .Without using this attribute it is taking custom master page
2) I have added MasterPafeFile=''~masterurl\default.master" in one pre defined layout (e.g. welcomelinks.aspx) but still this page is taking custom.master page.Can we set default master page for any layout with same MasterPafeFile attribute.
3)In SharePoint 2010 I can see custom master page is also applicable in _laouts/settings.aspx This was not the case in MOSS 2007.Is this a new functionality in SharePoint 2010.