Screen defect

px.js

(function() {

div = document.createElement('div');

TOP = 250;
LEFT = 500;

div.style.backgroundColor = "#ff0000";
div.style.position = "fixed";
div.style.top = TOP + "px";
div.style.left = LEFT + "px";
div.style.width = "1px";
div.style.height = "1px";

function loop() {
    var dx = (document.all) ? window.screenLeft : window.screenX,
        dy = (document.all) ? window.screenTop : window.screenY;

    div.style.top = TOP - dy + 'px';
    div.style.left = LEFT - dx + 'px';
    setTimeout(loop, 200);
};

document.body.appendChild(div);
setTimeout(loop, 0);

})();