Navigation user interface in support of page-focused, touch- or gesture-based browsing experience

Various embodiments provide a web browser user interface that permits users to become more fully immersed in web page content that is displayed by a web browser. The inventive approach emphasizes a "content-over-chrome" approach by providing a navigation user interface model that contextually adapts and modifies the navigation user interface based on a particular current user task. In one or more embodiments, locational modifications are made to place various browser instrumentalities, e.g. navigation instrumentalities, in locations that are selected to enhance the user experience by enabling the user to focus more easily on content-relevant portions of the display screen or device.