1.PlaceHolderQuickLaunchTop: The top of the Quick Launch menu
2.PlaceHolderQuickLaunchBottom: The bottom of the Quick Launch menu
3.PlacHolderPageTitle: The title of the site
4.PlaceHolderAdditionalPageHead: A placeholder in the head section of the page used to add extra components such as ECMAScript (Javascript, JScript) and Cascading Style Sheets (CSS)
5.OPlaceHolderBodyAreaClass: The class of the body area
6.PlaceHolderSiteName: Name of the site where the current page resides
7.PlaceHolderPageTitleInTitleArea: Title of the page, which appears in the title area on the page
8.PlaceHolderPageDescription: Description of the current page
9.PlaceHolderPageSearchArea: Section of the page for the search controls
10.PlaceHolderGlobalNavigation: Breadcremb control on the page
11.PlaceHolderTitleBreadcrumb: Breadcrumb text for the breadcrumb control
12.PlaceHolderGlobalNavigationSiteMap: List of subsites and sibling sites in the global navigation on the page
13.PlaceHolderTopNavBar: Container used to hold the top navigation bar
14.PlaceHolderHorizontalNav: Navigation menu that is inside the top navigation bar
15.PlaceHolderLeftNavBarDataSource: Placement of the data source used to populate the left navigation bar
16.PlaceHolderCalendarNavigator: Date picker used when a calendar is visible on tha page
17.PlaceHolderLeftNavBarTop: The top section of the left navigation bar
18.PlaceHolderLeftNavBar: The Quick Launch bar
19.PlaceHolderLeftActions: Additional objects above the Quick LAunch bar
20.PlaceHolderMain: The main content of the page.
21.PlaceHolderFormDigest: The container where the page's Form Digest control is stored
22.PlaceHolderUtilityContent: Additional content at the bottom of the page. This is outside of the form tag.
23.PlaceHolderTitleAreaClass: The class for the title area. This is now in the head tag. Any customizations that add a Web Part zone in a content tag to this placeholder will cause an error on the page