[Octane]

Ваш код из далекого прошлого.

var ie //@cc_on = true;
var xPos = 0, yPos = 0;
var element = document.documentElement || document.body;

function calc(side) {
	return (element["scroll" + side] || 0) - (element["client" + side] || 0);
}

function getPageX(event) {
	return event.clientX + calc('Left');
}

function getPageY(event) {
	return event.clientY + calc('Top');
}

document.onmousemove = function(event) {
	var event = event || window.event;
	if(ie) {
		xPos = getPageX(event);
		yPos = getPageY(event);
	} else {
		xPos = event.pageX;
		yPos = event.pageY;
	}
};