We've found that the performance of a website is one of the most important factors in increasing overall growth and usage. To help developers increase user engagement, we've released the quick transitions feature to improve the front-end performance of canvas page applications.
Quick transitions uses Ajax to change pages without reloading the entire frame. While it's enabled, important Facebook features like Chat, Search, and the Applications menu do not need to reload as a user views subsequent pages.
You can enable quick transitions on the Canvas tab in the application settings editor. If you have an FBML canvas page, you don't need to take any further steps. IFrame applications can also use this feature or use a custom approach. Read the quick transitions documentation for more information.