function changeHeader(){
	var t=setTimeout("changeHeader()", 5000);
//	img_num = Math.floor(Math.random() * image_url.length);
	img_num++;
	if(img_num == image_url.length){
		img_num = 1;
	}
	if(document.getElementById("banner_pic")){
		document.getElementById("banner_pic").src = image_url[img_num];
	}
}