function hide_and_display(content_id, img_id){
	var content = document.getElementById(content_id);
        var img = document.getElementById(img_id);

	if (content.style.display == 'none') {
		content.style.display = 'block';
                img.src = "images/chevron_up.jpg";
	} else {
		content.style.display = 'none';
                img.src = "images/chevron_down.jpg";
	}
}