Js 漂浮层

<div id="scrollDiv">放些文字或图片</div>
<script type="text/javascript">
    var x = 50,y = 60; 
    var xin = true, yin = true ;
    var step = 1 ;
    var delay = 10 ;
    var obj=document.getElementById("scrollDiv") ;
    /**//*<![CDATA[*/
    function closeDiv(){
        document.getElementById('scrollDiv').style.display='none';
    }
    function rollMethod() { 
        var L=T=0;
        var R= document.body.clientWidth-obj.offsetWidth ;
        var B = document.body.clientHeight-obj.offsetHeight ;
        obj.style.left = x + document.body.scrollLeft ;
        obj.style.top = y + document.body.scrollTop ;
        x = x + step*(xin?1:-1) ;    
        if (x < L) { xin = true; x = L} 
        if (x > R){ xin = false; x = R} 
        y = y + step*(yin?1:-1) 
        if (y < T) { yin = true; y = T } 
        if (y > B) { yin = false; y = B } 
        } 
        var itl= setInterval("rollMethod()", delay) ;
        obj.onmouseover=function(){clearInterval(itl)} ;
        obj.onmouseout=function(){itl=setInterval("rollMethod()", delay);
    } 
   /**//*]]>*/
</script>