Где моя ощибка?
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Документ без названия</title>
<style>
</style>
</head>
<body>
<form>
<input type="text" value="" onkeyup="aa(this)" />
<script>
function aa(elem){
if(elem.value.length >5 && elem.value.length <10){
elem.style.background='red'}
}
</script>
</form>
</body>
</html>