This article outlines a practical suggestion for storing and referencing content in multiple sites. Following this suggestion will help prevent errors and permissions issues for users referencing documents, media, web content, and more from multiple sites.
According to the original concept; web content, structures, templates, documents, vocabularies and categories, application display templates and DDLs were not intended to be shared across sites unless those entities belong to the global scope. From Liferay Portal 6.2 however, some display portlets like the asset publisher, and certain content types now allow to use the scope of another site, even if it is not the global one. Although this is useful in some cases, the current staging framework may not be able to replicate the same references in the live site properly. In order to avoid confusion and possible dependency issues due to cross-site references, if you would like to share content in multiple sites with staging enabled, it is recommended to place it in the global scope.
Publishing to live may not work according to the user's expectation if there are references to content that does not belong to that site or the global site. For more information, please see the corresponding article, Staging a Site that References Another Site.
Please note that the functionality for this has been changed in Liferay 7.0—New feature for Liferay 7: Sharing Content between Sites.