javascript最短的拖动代码[兼容FF]

发帖时无法插入可运行代码?
以下为程序代码:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" />  
<script language="JavaScript" type="text/javascript">  
var x,y  
var drag_=false  
var D=new Function('obj','return document.getElementById(obj);')  
var IE=new Function('','if(navigator.appName.indexOf("Explorer")>=0)return 1;if(navigator.appName.indexOf("Netscape")>=0)return 2')  
function Move_obj(obj){//1  
                     D(obj).onmousedown=function(e){drag_=true//4  
                              with(this){style.position="absolute";temp1=offsetLeft;temp2=offsetTop;//5  
                              if(IE()==1){x=event.clientX;y=event.clientY//6  
                                  document.onmousemove=function(e){//7  
                                        if(drag_==false)return false  
                                     with(this){style.left=temp1+event.clientX-x+"px";style.top=temp2+event.clientY-y+"px"}  
                                     }//7  
                              }//6  
                              if(IE()==2){x=e.pageX;y=e.pageY;//8  
                                  document.onmousemove=function(e){//9  
                                        if(drag_==false)return false  
                                     with(this){style.left=temp1+e.pageX-x+"px";style.top=temp2+e.pageY-y+"px"}  
                                     }//9  
                              }//8  
                        }//5  
           document.onmouseup=new Function("drag_=false")  
                     }//4  
}//1  
</script>  
<body>  
这个是可以拖动的层

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]