拖动DIV

var rDrag = {
 
 o:null,
 
 init:function(o){
  o.onmousedown = this.start;
 },
 start:function(e){
  var o;
  e = rDrag.fixEvent(e);
               e.preventDefault && e.preventDefault();
               rDrag.o = o = this;
  o.x = e.clientX - rDrag.o.offsetLeft;
                o.y = e.clientY - rDrag.o.offsetTop;
  document.onmousemove = rDrag.move;
  document.onmouseup = rDrag.end;
 },
 move:function(e){
  e = rDrag.fixEvent(e);
  var oLeft,oTop;
  oLeft = e.clientX - rDrag.o.x;
  oTop = e.clientY - rDrag.o.y;
  rDrag.o.style.left = oLeft + 'px';
  rDrag.o.style.top = oTop + 'px';
 },
 end:function(e){
  e = rDrag.fixEvent(e);
  rDrag.o = document.onmousemove = document.onmouseup = null;
 },
    fixEvent: function(e){
        if (!e) {
            e = window.event;
            e.target = e.srcElement;
            e.layerX = e.offsetX;
            e.layerY = e.offsetY;
        }
        return e;
    }
}
window.onload = function(){
        var obj = document.getElementById('draggable');
 rDrag.init(obj);
}