In the new Beta version of Google Analytics an interesting new feature has been added that gives a report on the speed pages take to load for end users. By default, this feature is not enabled and all page loads are shown with a speed of zero. Enabling the new feature requires a change in the tracking code.
Google provided a nice how to regarding the change required to setup Site Speed in their help documentation which explains the required change in the Google Analytics tracking code. If you're using the excellent Google Analytics module for Drupal 7 then you can enable the new Site Speed code very easily from the Drupal Admin interface.