function nextFeature(current) {
if (ajax) {
		var q = 'get_feature.php?current=' + encodeURIComponent(current) + '&direction=up';
		ajax.open('get',q,true);
		ajax.onreadystatechange = show_feature;
		ajax.send(null);
	}
}

function prevFeature(current) {
if (ajax) {
		var q = 'get_feature.php?current=' + encodeURIComponent(current) + '&direction=back';
		ajax.open('get',q,true);
		ajax.onreadystatechange = show_feature;
		ajax.send(null);
	}
}

function show_feature() {
	if ((ajax.readyState == 4) && (ajax.status == 200)) {
		var object = document.getElementById('f_block');
		object.innerHTML = ajax.responseText;
	}
}