I Have Proble In .scrollTop ! Please Help Me

I Have Proble In .scrollTop ! Please Help Me



jQuery(window).scroll(function() {
if (jQuery(document).scrollTop() > 310 && jQuery(document).scrollTop() < 1070)) {
jQuery('html body div#top_menu').css({'z-index':'10'});
}else {
jQuery('html body div#top_menu').css({'z-index':'-1'});
}
});


This Is My Codes , Why Dont Work ?? Please Give Me The Correct Code