function periodical(seconds, callback) {
	if(seconds == null) seconds = 30;
	timerHandler.delay(seconds);
	function timerHandler() {
		callback();
		timerHandler.delay(seconds);
	}
}

function setInnerHTML(elementName, url) {
	new Ajax.Request(url, {
		method: "get",
		requestHeaders: ['If-Modified-Since', '1 Jan 2000 00:00:00 GMT'],
		onSuccess: function(r) {
			var t = r.responseText;
			if(t == null || t == "") return;
			document.getElementById(elementName).innerHTML = t;
		}
	});
}