function show_news(id){
    news = document.getElementById('news_area'+id);
    bt = document.getElementById('news_nav'+id);
    for(i=1;i<=5;i++){
        if(i==id){
            news.style.display = "block";    // block
            bt.className = 'news_nav'+i+'a';
        } else {
            document.getElementById('news_area'+i).style.display = "none";
            document.getElementById('news_nav'+i).className = 'news_nav'+i;
        }
    }
}