pairar sobre um div afectar outro
//cube is directly inside the container:
#container:hover > #cube { background-color: yellow; }
//cube is next to (after containers closing tag) the container:
#container:hover + #cube { background-color: yellow; }
//If the cube is somewhere inside the container:
#container:hover #cube { background-color: yellow; }
//If the cube is a sibling of the container:
#container:hover ~ #cube { background-color: yellow; }
fazer a ação sobre o hover em outro elemento
#container:hover ~ #cube { background-color: yellow; }
no ecrã de passagem de outro div css
.showme {
display: none;
}
.showhim:hover .showme {
display: block;
}
<div class="showhim">HOVER ME
<div class="showme">hai</div>
</div>