var seconds = 15;
var status  = false;

function load() {
	window.setTimeout("animate()", seconds*1000);
}

function highlightGIF(img,status) {
	if (document.images) {
		var i,s;
		for (i = 0;i < document.images.length;i++) { 
			if (document.images[i].name == img) {
				s = document.images[i].src;
				s = s.substr(0, s.length-5);
				s = s + (status == false ? "a.gif" : "b.gif");
				document.images[i].src = s;
				return;
			}
		}
	}
}

function highlightJPG(img,status) {
	if (document.images) {
		var i,s;
		for (i = 0;i < document.images.length;i++) { 
			if (document.images[i].name == img) {
				s = document.images[i].src;
				s = s.substr(0, s.length-5);
				s = s + (status == false ? "a.jpg" : "b.jpg");
				document.images[i].src = s;
				return;
			}
		}
	}
}

function animate() {
	status = !status;
	highlightJPG("header",status);	

	window.setTimeout("animate()",seconds*1000);
}