.black {_x000D_
display:flex;_x000D_
flex-direction: column;_x000D_
height: 200px;_x000D_
background:grey_x000D_
}_x000D_
.message {_x000D_
background:yellow;_x000D_
width:200px;_x000D_
padding:10px;_x000D_
margin: auto auto;_x000D_
}
_x000D_
<div class="black">_x000D_
<div class="message">_x000D_
This is a popup message._x000D_
</div>_x000D_
</div>
_x000D_