function changeImage(num) {
	var total = 4;
	for(i=1; i<=total; i++)	{
		if(i == num){
			document.images["tab" + i].src = "images/news_tab" + num + "2.gif";
		} else {
			document.images["tab" + i].src = "images/news_tab" + i + "1.gif";
		}
	}
}
changeImage(1);