#bloc_a{
height:50px;
width:50px;
background-color: red;
position:absolute;
top: 30px;
left: 60px;
z-index:3;
}
#bloc_b{
height:50px;
width:50px;
background-color: yellow;
position:absolute;
top: 45px;
left: 75px;
z-index:2;
}
#bloc_c{
height:50px;
width:50px;
background-color: blue;
position:absolute;
top: 65px;
left: 90px;
z-index:1;
}
