If your users ever need to wait for page processing to be completed (e.g. background downloading, UI locking, calculations, etc), it is highly recommended to provide them with some form of visual feedback such as a progress indicator, or meter. This provides a positive user experience, by assuring them that the application is still functioning correctly and not frozen.
Click on the 'show activity indicator' button to dynamically display a visual indicator for a fixed period of time.
Duration: (seconds)
Click on the 'show progress' button to display a meter, that updates over an interval of time.