Originally Posted by DaleDe
From the wiki
Values are calculated with reference to a width property, which if not specified defaults to the page width or the previous width. There are 'margin-width' and 'padding-width' properties which can be specified with length units or as a percentage. Auto is also allowed which is the same as not specifying a width.
I'm sorry, but I'm not following the practical consequence of this... how is margin-width distinct from margin -top -bottom -right and -left values?