Margins are properties of elements, effectively rectangles relative to the edge of an element. Their values, like the computed values of all other properties, cannot be set on user agents. A useful effect is accomplished by setting margin used values to particular values. Then, the element displays with boxes that have the desired lengths and the individual boxes display with the desired margins. User agents can compute the used values for the margins for the element in question either by itself or by examining other elements on the page. The focus of this specification is on the computed values themselves, not the concrete values that provide the basis for computing the used values.
Every element has two margins. The margin-left and margin-right values denote the margins on the left and right, respectively, of the rendering box for the element in question in the normal flow.
Letting x, y, z, and a, b, c be the margin-left, margin-top, margin-right, and margin-bottom values for the element in question, respectively, the computed values for the margins for the box in question in the normal flow are:
The margin-bottom margin property is a division of the vertical distance between the bottom of the bottom margin of the box in question in the normal flow and the top of the top margin of the box in question in the normal flow. The margin-bottom property is always a positive number unless the value of the margin-bottom property for the box in question is a ‘’. (See the margin properties for complete details.) d2c66b5586