详细解析网页漂浮广告代码的含义

网页漂浮广图片特效，这种特效我们总是很喜欢，鼠标指向图片后图片停止移动。

<pre>
<div id="ad" style="position:absolute"><a href="http://www.cnwebshow.com">
<img src="/img/200406301.jpg" border="0"></a>
</div>
<script>
  var x = 50,y = 60
  var xin = true, yin = true
  var step = 1
  var delay = 10
  var obj=document.getElementById("ad")
  function floatAD() {
     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("floatAD()", delay)
 obj.onmouseover=function(){clearInterval(itl)}
 obj.onmouseout=function(){itl=setInterval("floatAD()", delay)}
</script>
</pre>