麻烦高手看一下,这段对联的JS,为什么放入页面后不能随滚动条上下移动
var   delta=0.8; 
 	var   collection; 
 	function   floaters()   { 
 		this.items	=   []; 
 		this.addItem	=   function(id,x,y,content) 
 				      { 
 					document.write( ' <DIV   id= '+id+ '   style= "Z-INDEX:   10;   POSITION:   absolute;      width:80px;   height:60px;left: '+(typeof(x)== 'string '?eval(x):x)+ ';top: '+(typeof(y)== 'string '?eval(y):y)+ ' ">  '+content+ ' </DIV>  ');  					 
 					var   newItem				=   {}; 
 					newItem.object			=   document.getElementById(id); 
 					newItem.x				=   x; 
 					newItem.y				=   y;   
 					this.items[this.items.length]		=   newItem; 
 				      } 
 		this.play	=   function() 
 				      { 
 					collection				=   this.items 
 					setInterval( 'play() ',30); 
 				      } 
 		} 
 		function   play() 
 		{ 
 			if(screen.width <=800) 
 			{ 
 				for(var   i=0;i <collection.length;i++) 
 				{ 
 					collection[i].object.style.display	=    'none '; 
 				} 
 				return; 
 			} 
 			for(var   i=0;i <collection.length;i++) 
 			{ 
 				var   followObj		=   collection[i].object; 
 				var   followObj_x		=   (typeof(collection[i].x)== 'string '?eval(collection[i].x):collection[i].x); 
 				var   followObj_y		=   (typeof(collection[i].y)== 'string '?eval(collection[i].y):collection[i].y);   
 				if(followObj.offsetLeft!=(document.body.scrollLeft+followObj_x))   { 
 					var   dx=(document.body.scrollLeft+followObj_x-followObj.offsetLeft)*delta; 
 					dx=(dx> 0?1:-1)*Math.ceil(Math.abs(dx)); 
 					followObj.style.left=followObj.offsetLeft+dx; 
 					}   
 				if(followObj.offsetTop!=(document.body.scrollTop+followObj_y))   { 
 					var   dy=(document.body.scrollTop+followObj_y-followObj.offsetTop)*delta; 
 					dy=(dy> 0?1:-1)*Math.ceil(Math.abs(dy)); 
 					followObj.style.top=followObj.offsetTop+dy; 
 					} 
 				followObj.style.display	=    ' '; 
 			} 
 		}	 
 	var   theFloaters		=   new   floaters(); 
 	// 
 	theFloaters.addItem( 'followDiv1 ', 'document.body.clientWidth-106 ',80, ' <a   href=http://www.red.net.cn/style/info/hosting.asp   target=_blank>  <img   src=http://www.knowsky.com/ad/100300.gif   width=100   height=300   border=0>  </a>     '); 
 	theFloaters.addItem( 'followDiv2 ',6,80, ' '); 
 	theFloaters.play();   
 我的网页中很简单。 
  <%@LANGUAGE= "VBSCRIPT "   CODEPAGE= "936 "%>  
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  <script   src= "/Index/JS/flag.js ">  </script>  
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