Михаил Р.

onchange = script [CT]
The onchange event occurs when a control loses the input focus and its value has been modified since gaining focus. This attribute applies to the following elements: INPUT, SELECT, and TEXTAREA.

if ("createEvent" in document) {
    var evt = document.createEvent("HTMLEvents");
    evt.initEvent("change", false, true);
    element.dispatchEvent(evt);
}
else
    element.fireEvent("onchange");

function cookie_test() {
	global $cookie_test;
	$cookie_test = false;

	# Определяем имя файла
	$url = parse_url($_SERVER['REQUEST_URI']);
	$path = pathinfo($url['path']);
	$basename = $path['basename'];

	if( !isset($_COOKIE[$basename]) ) $cookie_test = true;	
	setcookie( $basename, 1, time()+3600 );
}
add_action('init', 'cookie_test');

global $cookie_test;
if($cookie_test) echo "Страница еще не просмотрена!";