the problem is with your script tag and you are missing );
and by the way did you imported jQuery?
<script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript"></script>
<script>
$(document).ready(function (){
if(navigator.userAgent.toLowerCase().indexOf("android") > -1){
window.location.href = 'http://play.google.com/store/apps/details?id=com.truecaller&hl=en';
}
if(navigator.userAgent.toLowerCase().indexOf("iphone") > -1){
window.location.href = 'http://itunes.apple.com/lb/app/truecaller-caller-id-number/id448142450?mt=8';
}
});
</script>