Visualforce is commonly used to produce custom pages that override or supplement standard platform functionality. Visualforce pages can also be incorporated into any HTML markup through use of an iframe.
An iframe, or inline frame, nests an HTML document inside another HTML document. For more information, visit http://reference.sitepoint.com/html/iframe.
In this recipe, we will add a Visualforce page to a Salesforce sidebar component. This page will display the number of currently open cases in the organization, and will be styled and sized to fit seamlessly into the sidebar.
This recipe makes use of a custom controller, so this will need to be created before the Visualforce page.