[devote]

<div id="overel" style="position: absolute; top: 100px; left: 100px; width: 100px; height: 100px; background-color: #f00;"></div>
<script type="text/javascript">
    document.getElementById( 'overel' ).onmousemove = function( e ) {
        var e = e || window.event;
        ( e.target || e.srcElement ).innerHTML = "X: " + ( e.layerX || e.offsetX ) + ", Y: " +  ( e.layerY || e.offsetY );
    }
</script>