var listForOnm={
	$:function(id){return document.getElementById(id);}
	,tagArr:function(obj,name){return obj.getElementsByTagName(name);}
	,cutInAttribute:function(id,tagName,on,off){
		var arr=this.tagArr(this.$(id),tagName),len=arr.length,i;
		for(i=0;i<len;i++){
			arr[i].onmouseover=function(){this.className=on;}
			arr[i].onmouseout=function(){this.className=off;}
		}
	}
}
window.onload=function(){
	//(id:UL标签的ID,tagName:UL下的LI,on:高亮显示的样式,off:初始状态的样式)
	listForOnm.cutInAttribute('changbg','li','on','off');
}