<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Example</title>
<script type="text/javascript">
function onKeyDown(event) {
//event=fixEvent(event);
if(event.keyCode==38) {
alert('Стрелочка вверх!');
} else if(event.keyCode==40) {
alert('Стрелочка вниз!');
}
}
</script>
</head>
<body>
<input type="text" name="search" onkeydown="onKeyDown(event)">
</body>
</html>