How To Overlay One Div Over Another Div
Here we consider how to Overlay One Div Over Another Div.
You can overlay a Div on any other Div by using z-index and position Style.
Suppose we have two Div with ID FirstDiv and SecondDiv.

Following are the style applied for these Div.
#FirstDiv
{
width: 200px;
height: 200px;
background: red;
margin: 4px;
position: absolute;
}
#SecondDiv
{
width: 150px;
height: 150px;
background: blue;
position: absolute;
}
For making the Second Div Overlay on the FirstDiv, apply z-index : 1 for SecondDiv.
#SecondDiv
{
width: 150px;
height: 150px;
background: blue;
position: absolute;
z-index: 1;
}
By using z-index : 1 and position: absolute, we can overlay one Div over another.
In other words, the top Div should have greater z-index than the below Div.