To adjust Preview Pane Settings.
1) In the Preferences menu, go to General Settings under Contacts.
2) Choose to display either 20, 50, or 100 Contacts at a time in your view.
3) Turn the Preview Pane on or off: If the Preview Pane is enabled, the contact's details will appear under your contacts list. If it is disabled, contact details will be displayed in a pop-up window.
4) Click Save.