Before you begin working with custom layout updates, it is important to understand how the pages of your store are constructed, and the difference between the terms layout and layout update. Layout refers to the visual and structural composition of the page. Layout update refers to a specific set of XML instructions that can override or customize how the page is constructed.
The XML layout of your Magento store is a hierarchical structure of containers and blocks. Some elements appear on every page, and others appear only on specific pages. To learn more about layout, containers, and blocks, see Layout overview in our Frontend Developer Guide.
The Widget tool is an easy way to add an existing content block to the default layout of a page. For more advanced updates, you must save the XML layout update code on the server, and then reference the file as a custom layout update from the Admin. For an overview of the process, see Using Layout Updates.
In the following diagram, the names that refer to containers are black and the block types, or block class paths, are blue.
Standard block layout diagram
|page/html||The name of this block is
|page/html_head||The block name is
|page/html_notices||The block name is
|page/html_header||The block name is
|page/html_wrapper||Although included in the default layout, this block is deprecated and is included only to ensure backward compatibility. Do not use blocks of this type.|
|page/html_breadcrumbs||The name of this block is
|page/html_footer||The block name is
|page/template_links||There are two blocks of this type in the standard layout. The
Note: It is possible to manipulate the template links, as shown in the examples.
|page/switch||There are two blocks of this type in a standard layout. The
|core/messages||There are two blocks of this type in a standard layout. The
|core/text_list||This type of block is widely used throughout Magento as a placeholder for rendering children blocks.|
|core/profiler||There is only one instance of this type of block per page. It is used for the internal Magento profiler and should not be used for any other purpose.|