页面拖放的问题 不知道为什么就是实现不了功能 请好心人指点一下

// JavaScript Document
var obj,x,y,dx,dy;
function Setup(){
    if(!document.getElementByTagName) return;
    divs=document.getElementByTagName("DIV");
    for(i=;i<divs.length;i++){
        if(divs[i].className!="drag") continue;
        divs[i].onmousedown=Drag;
        }
        }
function Drag(e){
    if (!e) var e=window.event;
    obj=(e.target) ? e.target:e.srcElement;
    obj.style.borderColor="red";
    dx=x-obj.offsetLeft;
    dy=y-obj.offsetTop;
    }
function Move(e){
    if(!e) var e=window.event;
    if(e.pageX){
        x=e.pageX;
        y=e.pageY;
        }else if(e.clientX){
            x=e.clientX;
            y=e.clientY;
            }else return;
            if(obj){
                obj.style.left=x-dx;
                obj.style.top=y-dy;
                }
                }
function Drop(){
    if(!obj) return;
    obj.style.borderColor="black";
    obj=false;
    }
    document.onmousemove=Move;
    document.onmouseup=Drop;
    window.onload=Setup;