兼容FF/IE跟随鼠标的层的效果

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head> 
  <title></title> 
  <style type="text/css"> 
    #level{ 
      border: 1px solid #ccc; 
      background: #CCFFCC; 
      width:100px;height:30px; 
      position:absolute; 
    }

</style> 
  <script type="text/javascript"> 
    function addEvent(elm, evType, fn, useCapture) 
    { 
          if (elm.addEventListener){ 
            elm.addEventListener(evType, fn, useCapture); 
            return true; 
          } else if (elm.attachEvent){ 
            var r = elm.attachEvent("on"+evType, fn); 
            return r; 
          } else { 
            alert("Handler could not be removed"); 
          } 
    } 
    var x,y,t; 
    function doit(evt){ 
        var event=evt||window.event; 
        var level=document.getElementById("level"); 
        /*如果是第一次调用该函数level.style.left和level.style.top都为空，所以要初始化*/ 
        if(!level.style.left)level.style.left="1px"; 
        if(!level.style.top)level.style.top="1px"; 
        //用setTimeout函数调用该函数时event对象不存在，只有移动事件触发时event才存在 
        if(event){x=(event.x||event.pageX)}; 
        if(event){y=(event.y||event.pageY)}; 
        var theLeft=parseInt(level.style.left); 
        var theTop=parseInt(level.style.top); 
        if(x!=theLeft){ 
            if(theLeft<x){ 
                level.style.left=(theLeft+1)+"px"; 
            }else{ 
                level.style.left=(theLeft-1)+"px"; 
            } 
        }

if(theTop!=y){ 
            if(theTop<y){ 
                level.style.top=(theTop+1)+"px"; 
            }else{ 
                level.style.top=(theTop-1)+"px"; 
            } 
        } 
        if(x!=theLeft||y!=theTop) 
            setTimeout("doit()",100); 
    } 
    addEvent(document,"mousemove",doit); 
  </ script> 
</head> 
<body> 
<div id="level"> 
content 
</div> 
</body> 
</html>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]

兼容FF/IE跟随鼠标的层的效果_javascript技巧