function changeNews(button,content,number){
 var i=0;
 var buttonpieces = document.getElementsByName(button);
 var contentpieces = document.getElementsByName(content);
	for(i=0;i<buttonpieces.length;i++){
	buttonpieces[i].background="images/b2_index_pic_tcbg.gif";
	buttonpieces[i].className="table4";
	contentpieces[i].style.display="none";
	}
 buttonpieces[number-1].background="images/b2_index_pic_zxbsbg.gif";
 buttonpieces[number-1].className="cn";
 contentpieces[number-1].style.display="block";
}