var bPrev;
var btbPrev;
function hc(time,obj){
	if(bPrev==null){
		bPrev=document.getElementById("bbt").getElementsByTagName("li")[0]
	}
	if(btbPrev==null){
		btbPrev=document.getElementById("btb").getElementsByTagName("div")[0]
	}
	bPrev.className="";	
	btbPrev.style.display="none";
	obj.className="bbt_a";
	document.getElementById(time).style.display="block";
	bPrev=obj;
	btbPrev=document.getElementById(time);
}