For a handy reference I am listing all possible Content Place Holders in SharePoint pages. This list is obtained from here
| Content placeholder | Description |
|---|---|
| PlaceHolderBodyAreaClass | Additional body styles in the page header |
| PlaceHolderBodyLeftBorder | Border element for the main page body |
| PlaceHolderBodyRightMargin | Right margin of the main page body |
| PlaceHolderCalendarNavigator | Shows a date-picker for navigating in a calendar when a calendar is visible on the page |
| PlaceHolderFormDigest | The “form digest” security control |
| PlaceHolderGlobalNavigation | The global navigation breadcrumb |
| PlaceHolderHorizontalNav | Top navigation menu for the page |
| PlaceHolderLeftActions | Bottom of the left navigation area |
| PlaceHolderLeftNavBar | Left navigation area |
| PlaceHolderLeftNavBarBorder | Border element on the left navigation bar |
| PlaceHolderLeftNavBarDataSource | Data source for the left navigation menu |
| PlaceHolderLeftNavBarTop | Top of the left navigation area |
| PlaceHolderMain | Main content of the page |
| PlaceHolderMiniConsole | A place to show page-level commands, for example, WIKI commands such as Edit Page, History, and Incoming Links |
| PlaceHolderNavSpacer | The width of the left navigation area |
| PlaceHolderPageDescription | Description of the page contents |
| PlaceHolderPageImage | Page icon in the upper-left area of the page |
| PlaceHolderSearchArea | Search box area |
| PlaceHolderSiteName | Site name |
| PlaceHolderTitleAreaClass | Additional styles in the page header |
| PlaceHolderTitleAreaSeparator | Shows shadows for the title area |
| PlaceHolderTitleBreadcrumb | Main content breadcrumb area |
| PlaceHolderPageTitleInTitleArea | Page title shown immediately below the breadcrumbs |
| PlaceHolderTitleLeftBorder | Left border of the title area |
| PlaceHolderTitleRightMargin | Right margin of the title area |
| PlaceHolderTopNavBar | Top navigation area |
| PlaceHolderUtilityContent | Extra content at the bottom of the page |
| SPNavigation | Empty by default in Windows SharePoint Services 3.0. Can be used for additional page editing controls. |
| WSSDesignConsole | The page editing controls when the page is in Edit Page mode (in the browser, click Site Actions, and then click Edit Page) |
UPDATE: An excellent visual reference to above mentioned Content Place Holders can be found here
