【说站】css边距重叠是什么

       .neighbor{
height: 100px;
background: red;
}
.father{
background: #f436365e;
}
.child{
height: 100px;
margin-top: 10px;
background: #00800047;
}
<div>
this is neighbor
</div>
<div>
<div>
this is child
</div>
</div>

<style type="text/css">
.father{
background: #f436365e;
overflow: hidden;
}
.child{
height: 20px;
margin: 30px auto 30px;
background: #00800047;
}
</style>
<div>
<div>
this is child1
</div>
<div>
this is child2
</div>
<div>
this is child1
</div>
</div>