When the User first accesses a Portal page to which the portal Web 2.0 theme is assigned, the CSA aggregator is initialized via its Default.jsp, just like a traditional SSA theme. The initial page that is loaded contains only the basic HTML structure of the page. This has empty placeholders to indicate where the CSA aggregator should place the theme navigation elements, such as navigation menus, page tabs, side navigation tree, etc., and the content of the page itself, such as rows, columns and portlets.
After the page is initially loaded, subsequent user actions are handled by the CSA aggregator. Rather than updating and refreshing the entire page on every user interaction, the CSA aggregator only updates the parts of the page that have actually changed.
If the user interacts with a portlet, only that portlet with its new contents will be requested and updated on the page. If a user selects a new page from the theme navigation links, only the affected navigation elements are updated, and the new page contents are rendered.