(function() {

    window.onmousedown = handleMouseMove;

    function handleMouseMove(event) {

        event = event || window.event; // IE-ism

        console.log(event.clientX);

        moveDiv(event.clientX,event.clientY);

    }

})();

​

function moveDiv(x_pos,y_pos){

    var d = document.getElementById('myDiv');

    d.style.left = x_pos + "px";

    d.style.top = y_pos + "px";

}