<div class="div1">div1</div>
<div class="div2">div2</div>
<div class="footer"></div>

.div1{
    width: 70%;
    min-height: 150px;
    background: #ccc;
    float: left;
}
.div2{
    width: 30%;
    min-height: 150px;
    background: #c00;
    margin-left: 70%;
}
.footer{
    clear: left;
    background: #000;
    min-height: 50px;
}

width: 70%;
min-height: 150px;
background: #ccc;
float: left;

width: 30%;
min-height: 150px;
background: #c00;
float: right;