//这是JS代码部分
<script type="text/javascript">
window.onload=function(){
	var i=document.getElementsByTagName("li");
	for(var j=0;j<i.length;j++)
	{
	i[j].time=null;
	i[j].alpha=30;
	i[j].onmouseover=function(){
		Move(this,100);
		};
	i[j].onmouseout=function(){
		Move(this,30);
		};
	}
}

function Move(obj,setAlpha){
	clearInterval(obj.time);
	var speed=0;
	obj.time=setInterval(function(){
		if(obj.alpha==setAlpha)
		{clearInterval(obj.time)}
		if(obj.alpha>setAlpha)
		{speed=-10;}
		else
		{speed=10;}
		obj.alpha+=speed;
		obj.style.filter="alpha(opacity:"+obj.alpha+")";
		obj.style.opacity=obj.alpha/100;
		},30)
}
</script>

//希望能帮忙看看哪里有问题T-T