Charlie Salazar

It is ironic that it took web UIs so long to discover the elegance and simplicity of context. Since its dawn, HTML lacked the sophisticated widgets that are present on the desktop and web UIs were always considered more primitive and slow. Contextual, AJAX-based UIs actually seem faster because they do not reveal all possible choices to the user. Instead they focus on surfacing just the bits that are necessary and then surfacing more based on user gestures.A good example of context-based UIs can be found in modern video players. The controls in these apps are hidden until the user moves the mouse over the player. Depicted below is the player from Vimeo.

The Rise of Contextual User Interfaces - ReadWriteWeb