Taken from here
If you’ve spent much time in SharePoint Designer 2007, you know what content placeholders are, and you know that you need to understand them before you start modifying master pages on a SharePoint site.
For those of you who haven’t worked with content placeholders, here’s an overview…
A content placeholder is a piece of code (starts with <asp:ContentPlaceHolder… >) that exists on a master page. It works together with a piece of code called a content region (starts with <asp:Content… >) that exists on a content page. Content placeholders are used to designate parts of the master page that will display replaceable content, the content that originates from a content page. This is how master pages are able to serve as templates for other pages on your web site.
You establish the general look and feel of your site in a master page—the colors, logos, global navigation, header and footer information. Once you establish the look and feel on a master page, you designate parts of the page that will display unique content originating from a content page, such as corporate documents, company or team events, and business forms. As a SharePoint site, you also need to consider SharePoint collaboration features, like lists, libraries, and wikis. To integrate a master page with your content pages, you use content placeholders.
Where can I view, create, and manage content controls?
To see the content placeholders that are being used on your SharePoint site, open your site’s default master page in SharePoint Designer.
If you want to change the value of a content placeholder for your entire site, make the change to the default master page. If you want to change the content inside of a placeholder for a content page on your site, make the change to the content page.
What do content placeholders look like in SharePoint Designer?
When you open a master page in SharePoint Designer, you see this:
(Tip: You may need to turn on the Empty Containers and Visible Borders visual aids in Designer to view the master page this way.)
To view the default content placeholders, open the Master Page toolbar. You do this by clicking View > Toolbars > Master Page. A floating toolbar appears. Click the down arrow and then choose one of the content placeholders (see figure).
This highlights the content placeholder on the master page, which in this case is the PlaceHolderTitleBreadcrumbcontent control.
Okay enough. Show me a preview of these content placeholders
On a Windows SharePoint Services 3.0 master page (Default.master), there are 30 default content placeholders.
I’ve listed them below, along with a preview of what each content placeholder looks like on your final web pages. The preview is, in effect, a combination of the content placeholder from the master page and the contents of the corresponding content region from the content page. I’ve highlighted the content placeholder with a red outline to make it easier to see.
There are a few content placeholders that have no visual representation. For example, the PlaceHolderBodyAreaClass content placeholder serves as a placeholder for styles. I placed these content placeholders at the end, about where they appear on the master page.
PlaceHolderGlobalNavigationSiteMap
Site map used by the global navigation breadcrumb
Site map used by the global navigation breadcrumb
PlaceHolderGlobalNavigation
Global navigation breadcrumb
Global navigation breadcrumb
PlaceHolderSiteName
Site name
Site name
PlaceHolderSearchArea
Search box area
Search box area
PlaceHolderTopNavBar
Top navigation area
Top navigation area
PlaceHolderHorizontalNav
Top navigation menu for the page (defaults with the Home tab)
Top navigation menu for the page (defaults with the Home tab)
PlaceHolderPageImage
Page icon in the upper-left area of the page
Page icon in the upper-left area of the page
PlaceHolderCalendarNavigator
Date-picker for navigating a calendar, when enabled
Date-picker for navigating a calendar, when enabled
PlaceHolderTitleAreaSeparator
Displays shadows for the title area
Displays shadows for the title area
PlaceHolderLeftNavBarDataSource
Data source for the left navigation menu
Data source for the left navigation menu
PlaceHolderLeftNavBarTop
Top of the left navigation area
Top of the left navigation area
PlaceHolderLeftNavBar
Left navigation area (contains the Quick Launch)
Left navigation area (contains the Quick Launch)
PlaceHolderLeftNavBarBorder
Border element on the left navigation bar
Border element on the left navigation bar
PlaceHolderLeftActions
Bottom of the left navigation area
Bottom of the left navigation area
PlaceHolderPageTitleInTitleArea
Page title shown immediately below the breadcrumbs
Page title shown immediately below the breadcrumbs
PlaceHolderPageDescription
Description of the page contents
Description of the page contents
PlaceHolderTitleBreadcrumb
Main content breadcrumb area
Main content breadcrumb area
PlaceHolderTitleLeftBorder
Left border of the title area
Left border of the title area
PlaceHolderTitleRightMargin
Right margin of the title area
Right margin of the title area
PlaceHolderBodyLeftBorder
Border element for the main page body
Border element for the main page body
PlaceHolderMain
Main content of the page
Main content of the page
PlaceHolderBodyRightMargin
Right margin of the main page body
Right margin of the main page body
PlaceHolderMiniConsole
A place to show page-level commands (for example, the Edit Page, History, and Incoming Links WIKI commands)
A place to show page-level commands (for example, the Edit Page, History, and Incoming Links WIKI commands)
WSSDesignConsole
The page editing controls when the page is in Edit Page mode
The page editing controls when the page is in Edit Page mode
PlaceHolderNavSpacer
The width of the left navigation area
The width of the left navigation area
PlaceHolderFormDigest
The “form digest” security control
The “form digest” security control
PlaceHolderUtilityContent
Extra content at the bottom of the page
Extra content at the bottom of the page
SPNavigation
Used for additional page editing controls. (Empty by default in Windows SharePoint Services 3.0.)
Used for additional page editing controls. (Empty by default in Windows SharePoint Services 3.0.)
PlaceHolderBodyAreaClass
Additional body styles in the page header
Additional body styles in the page header
PlaceHolderTitleAreaClass
Additional styles in the page header
Additional styles in the page header
For more information
For more information on default content placeholders, including how to modify them in SharePoint Designer, see the article, Modify the default SharePoint content placeholders on Office Online.
All for now…