I have 3 divs in a row and then again 3 divs in another row like a grid.
I want to overlap div#4 on div#1, 
I have 3 divs in a row and then again 3 divs in another row like a grid.
I want to overlap div#4 on div#1, 
 
    
     
    
    You can try with one div having position absolute and other with position relative.
<div class="gray">
    <div class="blue">
    </div>
</div> 
.gray {
    background-color: #818181;
    height: 220px;
    width: 300px;
    position: absolute;
    overflow: hidden;
}
.blue {
    background-color: #0090ff;
    top: 0;
    height: 200px;
    width: 180px;
    position: relative;
    float:left;
    margin-left: 30px;
    margin-top: 10px;
}
