function keep_session() {
	var req = false;
	if (window.XMLHttpRequest) {
		req = new XMLHttpRequest();
		if (req.overrideMimeType) { req.overrideMimeType("text/plain"); }
	} else if (window.ActiveXObject) {
		try { req = new ActiveXObject("Msxml2.XMLHTTP"); } catch(e) {
			try { req = new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {}
		}
	}
	if ( ! req ) {
		return false;
	}
	req.onreadystatechange = function() { }
	req.open("GET", "sessions.php?"+Math.round(Math.random()*1000), true);
	req.send("");
}
setInterval("keep_session();", 60000*5);