2. View Medium: 770 pix wide Overlay.
Center-align the overlay vertically on the screen.
The overlay may or may not have the button bar at the bottom.
The button bar at the bottom is a persistent bar that should stay in place and not scroll up or down.
In the button bar, the 'Primary' button should be on the very right, and 'Back' or 'Cancel' should be on the very left. If there is a need for a secondary button, it should be placed to the left of the primary button.