sidebar widowshade?

on broken code > ‘catagories’ is windowshaded, or accordioned. WP search reveals no hits on either term, but i’m certain this is common knowledge, i’m just using not the ‘correct’ search term.

is there a plug-in or javascript effect available?

anyone point me in the right direction. tia. best…skip

( WP-default theme, WP 2.2)