Transition Div

Transition div from top to bottom of screen onload

HTML

<body onload="animateDiv()">
<div id='popup' class="popup-container"></div>
</body>

CSS

.popup-container{
	width:20%;
	height:200px;
	background-color:white;
	border: 2px solid black;
	position: absolute;
	left:40%;
	top:0px;
	transition: 2s;
}

JavaScript

function animateDiv(){
		var popup = document.getElementById("popup");
		popup.style.top = "100px";
	}