Clustering

Although I write CSS on a more-or-less daily basis,
I still regularly find myself using an incorrect syntax
that seems so natural to me that I simply fail to remember
that it is incorrect.  Time and again I find myself
writing defective CSS such as

	Foo.bar {margin-top, margin-bottom: 1ex}

only to belatedly remember that I am required to
either explicitly replicate the value, as in

	Foo.bar {margin-top: 1ex; margin-bottom: 1ex}

or (far worse) use the totally unmemorable shorthand

	Foo.bar {margin: ...}

where I invariably forget the order of the (upto) four values.

Given CSS allows me to cluster selectors, as in

	Foo.bar, Foo.baz {property: value; ...}

is there any fundamental reason why it could not
be extended to allow /properties/ to be clustered
in the same way ?

Philip TAYLOR