Вот база, остальное прикрутите
<style>
.div {
position: absolute;
left: 100px;
width: 20px;
height: 20px;
border: solid 3px navy;
}
</style>
<body>
<script>
window.onload = function () {
function move () {
var elem = document.createElement('div');
elem.className = 'div';
elem.style.top = '0px';
document.body.appendChild(elem);
var int = setInterval(function () {
var top = parseInt(elem.style.top);
if (top > 200) {
clearInterval(int);
document.body.removeChild(elem);
} else {
elem.style.top = top + 1 + 'px';
}
}, 10)
}
setInterval(function () {move()}, 1000);
}
</script>