version 2/101030 by Erik Temple
Section - UI anchor elements
An anchor-element is a kind of UI-element.
An anchor-element has a number called the horizontal margin. The horizontal margin is usually 999.
An anchor-element has a number called the vertical margin. The vertical margin is usually 999.
An anchor-element can be center-positioned, right-positioned, or left-positioned (this is its horizontal-positioning property).
An anchor-element can be bottom-positioned, central-positioned, or top-positioned (this is its vertical-positioning property).