function draggable(element) {    var dragging = null;    addListener(element, "mousedown", function(e) {        var e = window.event || e;        dragging = {            mouseX: e.clientX,            mouseY: e.clientY,            startX: parseInt(element.style.left),            startY: parseInt(element.style.top)        };        if (element.setCapture) element.setCapture();    });    addListener(element, "losecapture", function() {        dragging = null;    });    addListener(document, "mouseup", function() {        dragging = null;    }, true);    var dragTarget = element.setCapture ? element : document;    addListener(dragTarget, "mousemove", function(e) {        if (!dragging) return;        var e = window.event || e;        var top = dragging.startY + (e.clientY - dragging.mouseY);        var left = dragging.startX + (e.clientX - dragging.mouseX);        element.style.top = (Math.max(0, top)) + "px";        element.style.left = (Math.max(0, left)) + "px";    }, true);};draggable(document.getElementById("drag"));