<style> 
            #flashRight { POSITION: absolute; TOP: expression(lockTop());    LEFT:expression(lockLeft(false)); } 
            #flashLeft { POSITION: absolute; TOP: expression(lockTop());    LEFT:expression(lockLeft(true)); } 
        </style> 

        <script language="javascript"> 
        function lockTop() 
        { 
            var _body=document.body; 
            return _body.scrollTop; 
        }
        function lockLeft(left)
        {
            if(left)
            {
                return    (screen.availWidth - 777)/2 - 134;
            }
            else
            {
                return    (screen.availWidth - 777)/2 + 770;        
            }
        }
        </script> 

 可以看到代码也变得很简单

        <div id="flashRight">
            
         </div>
         <div id="flashLeft">
            
        </div>