function secChat(obj,ele,num){
  var cur=document.getElementById(obj).getElementsByTagName("li");
  for (var i=0;i< cur.length;i++){
  	  cur[i].className="";
	  document.getElementById(ele+"_"+i).style.display="none";
	}
   cur[num].className="Current";
   document.getElementById(ele+"_"+num).style.display="block";
}