2.1.56 [CSS-Level2-2009] Section 10.3.3, Block-level, non-replaced elements in normal flow

V0084:

The specification states:

 If all of the above have a computed value other than 'auto', the values are said to 
 be "over-constrained" and one of the used values will have to be different from its 
 computed value. If the 'direction' property of the containing block has the value 
 'ltr', the specified value of 'margin-right' is ignored and the value is calculated 
 so as to make the equality true. If the value of 'direction' is 'rtl', this happens 
 to 'margin-left' instead.

Quirks Mode (All Versions)

When one or more of the listed properties are "over-constrained" and the value of the direction property is ltr, the margin-right property is not adjusted. Instead, both margins and paddings are applied and the content box is reduced.

IE8 Mode (All Versions)

The value of the margin-left property is not recalculated and the value for margin-right is not set to 0 when the direction property is set to rtl.

V0216:

The specification states:

 The following constraints must hold among the used values of the other properties:
 'margin-left' + 'border-left-width' + 'padding-left' + 'width' + 'padding-right' + 
 'border-right-width' + 'margin-right' = width of containing block

Quirks Mode (All Versions)

The box model does not meet this constraint.

V0217:

The specification states:

 If there is exactly one value specified as 'auto', its used value follows from the 
 equality.

Quirks Mode (All Versions)

The box model does not respect the inequality defined in this section.

V0218:

The specification states:

 If both 'margin-left' and 'margin-right' are 'auto', their used values are equal. 
 This horizontally centers the element with respect to the edges of the containing 
 block.

Quirks Mode (All Versions)

When both margin-left and margin-right are auto, margin-left takes precedence when in RTL, and margin-right takes precedence when in LTR. This, in effect, consumes all of the available margin space that should be distributed equally between margin-left and margin-right.

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