Three-pane interface
Appearance
A Three-pane interface is a category of graphical user interface in which the screen or window is divided into three panes displaying information. This information typically falls into a hierarchal relationship of master-detail with an embedded inspector window. Microsoft's Outlook Express email client popularized a mailboxes / mailbox contents / email text layout that became the norm until web-based user interfaces rose in popularity during the mid 2000s.