Various embodiments utilize a layout viewport and a visual viewport separate from the layout viewport. The layout viewport is utilized for such things as page layout operations and reporting Document Object Model values to script. The layout viewport can be thought of as an initial rectangle which is equivalent in size to the initial containing block. The initial containing block is a containing block that contains web content that is initially visible to the user. The visual viewport is separate from the layout viewport and is allowed to be freely manipulated relative to the layout viewport. For example, the visual viewport may "push" the layout viewport around when it collides with the layout viewport boundaries. The visual viewport can be thought of as the rectangle that is visible to the user.