Negative Margins

HTML

<div id="a"></div>
<div id="b"></div>
<div id="c"></div>
<div id="d"></div>
<div id="e"></div>
<div id="f"></div>

CSS

div {
 width: 100px;
 height: 100px;
 border: solid 1px #000;
 opacity: 0.5;
}
#a {
  margin-top: -50px;
  background-color: grey;
}
#b {
  margin-bottom: -150px;
  background-color: yellow;
}
#c {
  background-color: blue;
}