visibility of elements

Wouldn't it be good if we had in the style-sheet specification a way to
specify the visibility of an element.

I think that we could have a new property named "visibility" that could
have 3 values: "invisible", "folded", "normal". 

If we had this feature in CSS, then one could specify that for instance 
that images are not visible (and so not loaded) for documents associated
with a CSS. With this feature, one could also tell that the lists of his
document are folded, when the document is loaded, so that the reader have
a more general view of the document when it first appears.

This functionnality relates to the presentation of documents and i really m
miss it to provide differents levels of reading to different users.