Brook,
как как?
<div style="background-color:rgba(0, 256, 150, 0.5);position:absolute; width:20px;height:20px;border:2px solid rgba(200, 100, 50, 0.8);" id="div"></div>
<script>
var div = document.getElementById("div");
div.onmouseover = function () {
this.style.top = Math.random() * 100;
this.style.left = Math.random() * 80;
}
</script>