具体代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
body,div{
margin:0;
padding:0;
}
#box{
position:relative;
margin:20px auto;
300px;
height:300px;
background:#008000;
}
#mark{
position:absolute;
top:0;
left:0;
100px;
height:100px;
background:red;
}
</style>
</head>
<body>
<div id='box'>
</div>
<script>
var box = document.getElementById('box');
box.onmouseover = function(e){
e = e || window.event;
var mark = document.createElement('div');
mark.id = "mark";
this.appendChild(mark);
mark.style.left = e.clientX - this.offsetLeft + 5 + "px";
mark.style.top = e.clientY - this.offsetTop + 5 + "px";
//阻止mark盒子的onmouseover事件的冒泡传播
mark.onmouseover = function(e){
e = e || window.event;
e.stopPropagation ? e.stopPropagation():e.cancelBubble = true;
}
mark.onmouseout = function(e){
e = e || window.event;
e.stopPropagation ? e.stopPropagation():e.cancelBubble = true;
}
}
//以下代码会出现一个问题，当鼠标移动过快的时候，鼠标会进入到mark这个盒子，会触发它的mouseover行为，由于事件的冒泡传播机制，导致box的mouseover会重新被触发，导致红色盒子一直在不断的创建
box.onmousemove = function(e){
e = e || window.event;
var mark = document.getElementById('mark');
if(mark){
mark.style.left = e.clientX - this.offsetLeft + 5 + "px";
mark.style.top = e.clientY - this.offsetTop + 5 + "px";
}
}
//依然有问题：鼠标快速移动，首先会到mark上，此时浏览器在计算mark的位置，计算完成，mark到达指定的位置，此时鼠标又重新回到box上，触发了box的mouseover，也触发了mark的mouseout，也会传播到box的mouseout上，会把mark先删除，然后在创建
box.onmouseout = function(e){
e = e || window.event;
var mark = document.getElementById('mark');
if(mark){
this.removeChild(mark);
}
}
//上面代码也可以通过将over和out事件分别改为enter和leave
//onmouseenter和onmouseover都是鼠标滑上去的行为，但是onmouseenter浏览器默认阻止了它的冒泡传播（mark的onmouseenter行为触发，不会传播到box）；而onmouseover是存在冒泡传播的，想要阻止的话需要手动阻止
</script>
</body>
</html>