Visual weight in User Interface Design
When it comes to balance, the physical world tells us that weight is associated with gravity and objects being pulled downward. Visual weight, however, is more 3-dimensional in that it asserts itself in other directions as well. The visual weight each object carries pushes some UI elements to the forefront while causing others to recede. The process of assigning weight to different screen elements and graphics based on importance creates a successful visual hierarchy that controls which elements a user sees in what order.