From my testing using this CSS:
.expandable{
display: none;
}
.expand:hover+.expandable{
display:inline !important;
}
.expandable:hover{
display:inline !important;
}
And this HTML:
, it resulted that it does expand using the second , but does not expand using the first one. So if there is a div between the hover target and the hidden div, then it will not work.