CEGUI has two positioning methods.
The unified positioning and absolute.
with the unified system you can align
the window to the left/right/top/bottom/center
side und use an relative offset to
define the distance to the border.
you can also use exact pixel offsets,
or a mix between relative and absolute
positioning sizing is possible too.
So yes, you can position your widgeds
resolution independent - or, if you don't like
this - not.

The premade skins are ugly, so I created a Win7 lookalike
skin.