Show %
<!DOCTYPE html><html>
<head>
<style>
.bg{
background-color:cyan;
}
</style>
</head>
<body>
<div id="area" class="bg" onmouseover="showCoords(event)">
out
</div>
<script>
function showCoords(event) {
var x = event.clientX;
var xPercent = x/window.innerWidth;
document.getElementById("area").innerHTML = parseInt(xPercent*100)+"%";
}
</script>
</body>
</html>