RE: [css21][css3-background] background-position examples conflict with prose/grammar

> From: L. David Baron [mailto:dbaron@dbaron.org]
 
> Note the "and at least one value is not a keyword".  Two keywords
> together are allowed in either order, as long as one can be
> interpreted as horizontal and the other can be interpreted as
> vertical.  ('center' can be interpreted as either.)
> 
> The grammar also allows this in the '&&' (our special notation for
> both required, but in either order) that's in the third part of the
> top-level |.

Thanks ! Now that you've clarified it, I think I recall a f2f discussion 
about this. In my mind though, "at least one" does not exclude "both". May 
I suggest this be clarified with explicit prose ? E.g.

Update:

#If two values are given and at least one value is not a keyword, then the first value represents the horizontal position #(or offset) and the second represents the vertical position (or offset). <percentage> and <length> values here represent an #offset of the top left corner of the background image from the top left corner of the background positioning area.

...to:

#If two values are given and one value is not a keyword, then the first value represents the horizontal position #(or #offset) and the second represents the vertical position (or offset). <percentage> and <length> values here represent an #offset of the top left corner of the background image from the top left corner of the background positioning area. If both
#values are keywords, the vertical and horizontal component can be specified in either order.