.ex4 {position: relative;
width: 200px;
height: 200px;
border: 1px solid #7a7a7a;
float:left;
margin:10px;
}
.ex4 div {
position: absolute;
width: 100px;
height: 20px;
padding-top:80px;
vertical-align:baseline;
color:#fff;
}
.ex4 div:nth-child(1) {
left:10px;
top:10px;
background-color: cadetblue
}
.ex4 div:nth-child(2) {
left:30px;
top:30px;
background-color: darkgreen
}
.ex4 div:nth-child(3) {
left:50px;
top:50px;
background-color: darkorange
}
.ex4 div:nth-child(4) {
left:70px;
top:70px;
background-color: cornflowerblue
}
.z5 {z-index: 10;}
.z6 {z-index: 7;}
.z7 {z-index: 5;}
.z8 {z-index: 3;}
<!DOCTYPE html>
<html lang="ko">
<head></head>
<body>
<div class="ex4">
<div class="z1">1</div>
<div class="z2">2</div>
<div class="z3">3</div>
<div class="z4">4</div>
</div>
<div class="ex4">
<div class="z5">1</div>
<div class="z6">2</div>
<div class="z7">3</div>
<div class="z8">4</div>
</div>
</body>
</html>