In this example, each <li> is set to have no bullet displayed. When hovered over, list-style type is set to "disc" (though it could be an image or any other bullet). On "mouseout", the bullet doesn't disappear (list- style-type does not revert to "none"). Similarly, if a bullet is set to disc by default, a :hover setting of "none" won't make the bullet disappear on rollover.
This is a duplicate of: http://bugzilla.opendarwin.org/show_bug.cgi?id=4855
*** This bug has been marked as a duplicate of 4855 ***