margin top to div inside another div

margin top to div inside another div

I have two divs wich has background image and I would like to add margin
to the the 2nd div but it is creating white space. How can I add top
margin while keeping the div inside the other div.
<div class="background">
<div class="logo">
</div>
</div>
.logo{background-image: url(image/logo2.png);
height:40px;
width:400px;
margin-left:100px;
display:block;
margin-top:20px;
}
.background{
background-image: url(image/empback.png);
width:100%;
height:94px;
min-width:1345px;
}