<div class="div1">1</div>
<div class="div2">2</div>
<div class="div3">3</div>
div{
width:100px;
height:100px;
font-size:40px;
line-height:100px;
color:#fff;
text-align:center;
}
.div1{
background:red;
margin:0 auto;
}
.div2{
background: green;
float:left;
margin-left: 50%;
}
.div3{
background: blue;
float:left;
margin-left: -200px;
}